refactor(account): replace JVM-only APIs in Account's group with KMP ones

So the group can land in commons/commonMain rather than jvmAndroid:

- java.math.BigDecimal -> quartz.utils.BigDecimal (Account, AccountZapActions);
  on JVM/Android it is a typealias for the same class.
- java.util.UUID.randomUUID() -> kotlin.uuid.Uuid.random() (AccountSettings,
  FollowSetsState, StarterPacksState); same random v4 string form.
- java.util.Base64 -> kotlin.io.encoding.Base64 (OtsState); both are the
  RFC 4648 alphabet with padding.
- ConcurrentHashMap -> quartz ConcurrentMap and Collections.synchronizedSet
  -> commons ConcurrentSet (GeohashChatIdentityState, AccountConcordActions);
  only get/set/remove and an atomic add are used.
- Locale.getDefault().language -> commons getDefaultLanguageCode(), a new
  expect beside getLanguagesSpokenByUser (Android/JVM: the same call; iOS:
  NSLocale.currentLocale.languageCode).

CashuWalletState's maps are iterated (keys/values/entries), which
ConcurrentMap does not offer; they change with the rest of the Cashu
promotion. No behaviour change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S7FuNBSKiyVecARSoE4B9P

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -341,6 +341,7 @@ import com.vitorpamplona.quartz.nipA0VoiceMessages.VoiceReplyEvent
 import com.vitorpamplona.quartz.nipA3PaymentTargets.PaymentTarget
 import com.vitorpamplona.quartz.nipB0WebBookmarks.WebBookmarkEvent
 import com.vitorpamplona.quartz.nipC7Chats.ChatEvent
+import com.vitorpamplona.quartz.utils.BigDecimal
 import com.vitorpamplona.quartz.utils.DualCase
 import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.RandomInstance
@@ -362,7 +363,6 @@ import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
-import java.math.BigDecimal
 import kotlin.coroutines.cancellation.CancellationException
 import com.vitorpamplona.quartz.experimental.nip95.header.thumbhash as nip95thumbhash
 import com.vitorpamplona.quartz.experimental.profileGallery.thumbhash as galleryThumbhash

amethyst/src/main/java/com/vitorpamplona/amethyst/model/AccountConcordActions.kt

@@ -30,6 +30,7 @@ import com.vitorpamplona.amethyst.commons.model.cache.filter
 import com.vitorpamplona.amethyst.commons.model.concord.ConcordChannel
 import com.vitorpamplona.amethyst.commons.model.concord.ConcordCommunitySession
 import com.vitorpamplona.amethyst.commons.model.concordChannelLastReadRoute
+import com.vitorpamplona.amethyst.commons.util.ConcurrentSet
 import com.vitorpamplona.amethyst.commons.viewmodels.ReplyMode
 import com.vitorpamplona.quartz.concord.cord02Community.ConcordCommunityList.withControlRoot
 import com.vitorpamplona.quartz.concord.cord02Community.ConcordCommunityListEntry
@@ -70,10 +71,10 @@ import com.vitorpamplona.quartz.nipC7Chats.ChatEvent
 import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.RandomInstance
 import com.vitorpamplona.quartz.utils.TimeUtils
+import com.vitorpamplona.quartz.utils.concurrent.ConcurrentMap
 import kotlinx.coroutines.async
 import kotlinx.coroutines.awaitAll
 import kotlinx.coroutines.coroutineScope
-import java.util.concurrent.ConcurrentHashMap
 
 /** Name of the default Concord community Admin role minted by "Make admin". */
 private const val CONCORD_ADMIN_ROLE = "Admin"
@@ -1222,7 +1223,7 @@ class AccountConcordActions(
     // Rotations we've already adopted ("communityId:epoch"), so a base-rekey wrap still buffered
     // in the pre-rebuild window (the session rebuild off `liveCommunities` is async) is not
     // adopted — and re-published — twice on successive revision ticks.
-    private val adoptedConcordRotations = java.util.Collections.synchronizedSet(HashSet<String>())
+    private val adoptedConcordRotations = ConcurrentSet<String>()
 
     /**
      * Persist a rotated access root/epoch for [entry], keeping the prior root as a
@@ -1341,7 +1342,7 @@ class AccountConcordActions(
     // Last time we re-resolved each community's invite_ref, so the recovery sweep rides the
     // Concord revision tick (which fires on every structural change) without turning it into a
     // relay-fetch loop.
-    private val lastConcordRecoveryCheck = ConcurrentHashMap<String, Long>()
+    private val lastConcordRecoveryCheck = ConcurrentMap<String, Long>()
 
     /**
      * Stranded recovery (CORD-05/06 receive path). A Refounding carries only

amethyst/src/main/java/com/vitorpamplona/amethyst/model/AccountSettings.kt

@@ -18,6 +18,8 @@
  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
+@file:OptIn(ExperimentalUuidApi::class)
+
 package com.vitorpamplona.amethyst.model
 
 import androidx.compose.runtime.Stable
@@ -92,6 +94,8 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.update
 import kotlinx.serialization.Serializable
+import kotlin.uuid.ExperimentalUuidApi
+import kotlin.uuid.Uuid
 
 val DefaultSignerPermissions =
     listOf(
@@ -596,9 +600,7 @@ class AccountSettings(
                 val entry =
                     NwcWalletEntryNorm(
                         id =
-                            java.util.UUID
-                                .randomUUID()
-                                .toString(),
+                            Uuid.random().toString(),
                         name = "Wallet",
                         uri = newServer,
                     )

amethyst/src/main/java/com/vitorpamplona/amethyst/model/AccountSyncedSettingsInternal.kt

@@ -23,10 +23,10 @@ package com.vitorpamplona.amethyst.model
 import com.vitorpamplona.amethyst.commons.model.navigation.BottomBarEntry
 import com.vitorpamplona.amethyst.commons.model.navigation.DefaultBottomBarEntries
 import com.vitorpamplona.amethyst.commons.service.pow.PoWCategory
+import com.vitorpamplona.amethyst.commons.util.getDefaultLanguageCode
 import com.vitorpamplona.amethyst.commons.util.getLanguagesSpokenByUser
 import com.vitorpamplona.quartz.nip57Zaps.ZapReceiptEvent
 import kotlinx.serialization.Serializable
-import java.util.Locale
 
 val DefaultReactions =
     listOf(
@@ -204,7 +204,7 @@ class AccountZapPreferencesInternal(
 class AccountLanguagePreferencesInternal(
     var dontTranslateFrom: Set<String> = getLanguagesSpokenByUser(),
     var languagePreferences: Map<String, String> = mapOf(),
-    var translateTo: String = Locale.getDefault().language,
+    var translateTo: String = getDefaultLanguageCode(),
 )
 
 @Serializable

amethyst/src/main/java/com/vitorpamplona/amethyst/model/AccountZapActions.kt

@@ -50,9 +50,9 @@ import com.vitorpamplona.quartz.nip57Zaps.ZapReceiptEvent
 import com.vitorpamplona.quartz.nip57Zaps.ZapRequestEvent
 import com.vitorpamplona.quartz.nipB1Bolt12Zaps.builder.Bolt12ZapBuilder
 import com.vitorpamplona.quartz.nipB1Bolt12Zaps.verify.Bolt12ZapValidation
+import com.vitorpamplona.quartz.utils.BigDecimal
 import com.vitorpamplona.quartz.utils.Log
 import kotlinx.coroutines.launch
-import java.math.BigDecimal
 import kotlin.coroutines.cancellation.CancellationException
 
 private const val ONCHAIN_BACKEND_NOT_CONFIGURED = "Bitcoin chain backend is not configured"

amethyst/src/main/java/com/vitorpamplona/amethyst/model/GeohashChatIdentityState.kt

@@ -28,11 +28,11 @@ import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
 import com.vitorpamplona.quartz.utils.RandomInstance
+import com.vitorpamplona.quartz.utils.concurrent.ConcurrentMap
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
-import java.util.concurrent.ConcurrentHashMap
 
 /**
  * The account's anonymous, per-geohash chat identities.
@@ -66,7 +66,7 @@ class GeohashChatIdentityState(
      * `synchronized`, because the store reads it protects are suspending.
      */
     private val mutex = Mutex()
-    private val cache = ConcurrentHashMap<String, KeyPair>()
+    private val cache = ConcurrentMap<String, KeyPair>()
 
     @Volatile private var loaded: GeohashIdentitySecrets? = null
 

amethyst/src/main/java/com/vitorpamplona/amethyst/model/nip03Timestamp/OtsState.kt

@@ -32,7 +32,7 @@ import com.vitorpamplona.quartz.utils.TimeUtils
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
-import java.util.Base64
+import kotlin.io.encoding.Base64
 
 class OtsState(
     val signer: NostrSigner,
@@ -58,7 +58,7 @@ class OtsState(
         Log.d("Pending Attestations") { "Updating ${settings.pendingAttestations.value.size} pending attestations" }
 
         return settings.pendingAttestations.value.toList().mapNotNull { (key, value) ->
-            val otsState = OtsEvent.upgrade(Base64.getDecoder().decode(value), key, otsResolver())
+            val otsState = OtsEvent.upgrade(Base64.decode(value), key, otsResolver())
 
             if (otsState != null) {
                 val hint = cache.getNoteIfExists(key)?.toEventHint<Event>()
@@ -93,7 +93,7 @@ class OtsState(
         settings.addPendingAttestation(
             id = id,
             stamp =
-                Base64.getEncoder().encodeToString(
+                Base64.encode(
                     OtsEvent.stamp(
                         id,
                         otsResolver(),

amethyst/src/main/java/com/vitorpamplona/amethyst/model/nip51Lists/followSets/FollowSetsState.kt

@@ -18,6 +18,8 @@
  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
+@file:OptIn(ExperimentalUuidApi::class)
+
 package com.vitorpamplona.amethyst.model.nip51Lists.followSets
 
 import com.vitorpamplona.amethyst.commons.model.AddressableNote
@@ -55,7 +57,8 @@ import kotlinx.coroutines.flow.onStart
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.transformLatest
 import kotlinx.coroutines.flow.update
-import java.util.UUID
+import kotlin.uuid.ExperimentalUuidApi
+import kotlin.uuid.Uuid
 
 /**
  * Maintains several stateflows for each step in processing PeopleLists
@@ -205,7 +208,7 @@ class FollowSetsState(
         isPrivate: Boolean = false,
         account: Account,
     ): String {
-        val dTag = UUID.randomUUID().toString()
+        val dTag = Uuid.random().toString()
         val newListTemplate =
             FollowSetEvent.build(
                 dTag = dTag,
@@ -253,7 +256,7 @@ class FollowSetsState(
     ) {
         val newList =
             FollowSetEvent.createListWithDescription(
-                dTag = UUID.randomUUID().toString(),
+                dTag = Uuid.random().toString(),
                 title = customCloneName ?: currentPeopleList.title,
                 description = customCloneDescription ?: currentPeopleList.description,
                 publicMembers = currentPeopleList.publicMembers.toUserTags(),

amethyst/src/main/java/com/vitorpamplona/amethyst/model/nip51Lists/followSets/StarterPacksState.kt

@@ -18,6 +18,8 @@
  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
+@file:OptIn(ExperimentalUuidApi::class)
+
 package com.vitorpamplona.amethyst.model.nip51Lists.followSets
 
 import com.vitorpamplona.amethyst.commons.model.AddressableNote
@@ -58,7 +60,8 @@ import kotlinx.coroutines.flow.onStart
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.transformLatest
 import kotlinx.coroutines.flow.update
-import java.util.UUID
+import kotlin.uuid.ExperimentalUuidApi
+import kotlin.uuid.Uuid
 
 /**
  * Maintains several stateflows for each step in processing PeopleLists
@@ -195,7 +198,7 @@ class StarterPacksState(
         isPrivate: Boolean = false,
         account: Account,
     ): String {
-        val dTag = UUID.randomUUID().toString()
+        val dTag = Uuid.random().toString()
 
         val newListTemplate =
             StarterPackEvent.build(
@@ -245,7 +248,7 @@ class StarterPacksState(
         val template =
             listEvent.update {
                 // new list
-                dTag(UUID.randomUUID().toString())
+                dTag(Uuid.random().toString())
 
                 // updates names
                 if (customCloneName != null) title(customCloneName)

commons/src/androidMain/kotlin/com/vitorpamplona/amethyst/commons/util/SpokenLanguages.android.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.commons.util
 
 import android.content.res.Resources
 import androidx.core.os.ConfigurationCompat
+import java.util.Locale
 
 actual fun getLanguagesSpokenByUser(): Set<String> {
     val languageList = ConfigurationCompat.getLocales(Resources.getSystem().configuration)
@@ -31,3 +32,5 @@ actual fun getLanguagesSpokenByUser(): Set<String> {
     }
     return codedList
 }
+
+actual fun getDefaultLanguageCode(): String = Locale.getDefault().language

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/util/SpokenLanguages.kt

@@ -25,3 +25,6 @@ package com.vitorpamplona.amethyst.commons.util
  * device, in no particular order. New accounts default to not translating from these.
  */
 expect fun getLanguagesSpokenByUser(): Set<String>
+
+/** The ISO 639 code of the device's current language, the default target for translations. */
+expect fun getDefaultLanguageCode(): String

commons/src/iosMain/kotlin/com/vitorpamplona/amethyst/commons/util/SpokenLanguages.ios.kt

@@ -21,6 +21,8 @@
 package com.vitorpamplona.amethyst.commons.util
 
 import platform.Foundation.NSLocale
+import platform.Foundation.currentLocale
+import platform.Foundation.languageCode
 import platform.Foundation.preferredLanguages
 
 // preferredLanguages holds BCP 47 tags ("pt-BR", "zh-Hans-CN"); the language code is the first subtag.
@@ -29,3 +31,5 @@ actual fun getLanguagesSpokenByUser(): Set<String> =
         .mapNotNull { (it as? String)?.substringBefore('-')?.lowercase() }
         .filter { it.isNotEmpty() }
         .toSet()
+
+actual fun getDefaultLanguageCode(): String = NSLocale.currentLocale.languageCode

commons/src/jvmMain/kotlin/com/vitorpamplona/amethyst/commons/util/SpokenLanguages.jvm.kt

@@ -24,3 +24,5 @@ import java.util.Locale
 
 // The JVM exposes one default locale, not the OS's ordered preference list.
 actual fun getLanguagesSpokenByUser(): Set<String> = setOf(Locale.getDefault().language)
+
+actual fun getDefaultLanguageCode(): String = Locale.getDefault().language