feat(nutzap): progress bar during send, matching lightning UX

The cashu zap chip previously fired its async send and closed the
popup with no visible motion until the kind:9321 round-tripped
back (1-2 seconds of "did the tap register?" silence). Wire the
same zappingProgress channel the lightning path uses so the bar
visibly animates from tap to completion.

Pieces:

- CashuWalletOps.sendNutzap: optional `onProgress: (Float) -> Unit`
  emitting at the network checkpoints — 0.55 after the swap (the
  long mint round-trip), 0.80 after the kind:9321 publish (the
  recipient can see it), 0.95 after keep + delete, 1.0 after the
  kind:7376 history.

- CashuWalletState.sendNutzap: forwards onProgress to ops and
  also emits 0.20 after scrubLocallyStaleProofs so the bar moves
  before the slow swap call begins.

- AccountViewModel.sendNutzap: accepts an `onProgress: (Float) -> Unit`
  parameter (default no-op so existing callers compile unchanged)
  and threads it through to CashuWalletState.

- ReactionsRow.onNutzap callback: emits 0.05 immediately on tap
  for instant click feedback, then passes the same `onProgress`
  channel the lightning chip uses so zappingProgress drives the
  same progress indicator. The existing onError reset already
  zeroes the bar on failure.

Resulting cadence at the UI:
  tap → 0.05 (instant)
       → 0.20 (scrub done)
       → 0.55 (mint swap done)
       → 0.80 (kind:9321 out)
       → 0.95 (token rollover + NIP-09 out)
       → 1.00 (history out, bar hides).

amethyst/src/main/java/com/vitorpamplona/amethyst/model/nip60Cashu/CashuWalletOps.kt

@@ -616,6 +616,7 @@ class CashuWalletOps(
         zappedEvent: EventHintBundle<out Event>,
         message: String,
         available: List<TokenEntry>,
+        onProgress: ((Float) -> Unit)? = null,
     ): NutzapSent {
         if (amountSats <= 0) throw IllegalArgumentException("Amount must be positive")
         seedWarmer()
@@ -628,6 +629,10 @@ class CashuWalletOps(
                 recipientP2pkPubkeyHex = recipientP2pkPubkeyHex,
                 targetSplit = amountSats,
             )
+        // Mint round-trip done — biggest chunk of the wall clock. Surface
+        // visible motion here so the user knows the click registered even
+        // before the recipient sees the kind:9321.
+        onProgress?.invoke(0.55f)
 
         // Build the kind:9321 first so we have its id to reference from history.
         val proofJsons = swap.send.map { nutzapProofJson.encodeToString(NutzapProofJson.serializer(), it.toNutzapJson()) }
@@ -642,6 +647,8 @@ class CashuWalletOps(
             )
         val nutzapEvent = signer.sign(nutzapTemplate)
         publish(nutzapEvent)
+        // kind:9321 is out — recipient's auto-redeem can fire from here.
+        onProgress?.invoke(0.80f)
 
         // Roll over change locally if any.
         val keepEvent =
@@ -663,6 +670,7 @@ class CashuWalletOps(
                     publish(it)
                 }
             }
+        onProgress?.invoke(0.95f)
 
         val historyTemplate =
             CashuSpendingHistoryEvent.build(
@@ -677,6 +685,7 @@ class CashuWalletOps(
             )
         val historyEvent = signer.sign(historyTemplate)
         publish(historyEvent)
+        onProgress?.invoke(1.0f)
 
         return NutzapSent(
             nutzapEvent = nutzapEvent,

amethyst/src/main/java/com/vitorpamplona/amethyst/model/nip60Cashu/CashuWalletState.kt

@@ -1021,6 +1021,7 @@ class CashuWalletState(
         recipientPubKey: HexKey,
         zappedEvent: EventHintBundle<out Event>,
         message: String = "",
+        onProgress: ((Float) -> Unit)? = null,
     ): NutzapSent {
         check(started) { "CashuWalletState.start() not called" }
         val target =
@@ -1033,6 +1034,10 @@ class CashuWalletState(
         // partial-failure persists until the user clicks send. Heal
         // first so the selection below works on a known-fresh view.
         scrubLocallyStaleProofs(target.mintUrl)
+        // First on-network step done. The caller already showed an
+        // instant 0.05 when the chip was tapped; lift to 0.20 here so
+        // the bar visibly moves even before the (slow) swap call.
+        onProgress?.invoke(0.20f)
 
         val available = _tokenEntries.value.filter { it.content.mint == target.mintUrl }
         if (available.isEmpty()) {
@@ -1047,6 +1052,7 @@ class CashuWalletState(
             zappedEvent = zappedEvent,
             message = message,
             available = available,
+            onProgress = onProgress,
         )
     }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/ReactionsRow.kt

@@ -2012,11 +2012,16 @@ fun ZapAmountChoicePopup(
                 nutzapAmountChoices = if (nutzapEnabled) zapAmountChoices else persistentListOf(),
                 onNutzap = { amountInSats ->
                     onZapStarts()
+                    // Instant click feedback. Without this initial nudge
+                    // the bar stays flat for ~1s until scrubLocallyStale-
+                    // Proofs returns; the user thinks the tap was lost.
+                    onProgress(0.05f)
                     accountViewModel.sendNutzap(
                         baseNote = baseNote,
                         amountSats = amountInSats,
                         message = "",
                         onError = onError,
+                        onProgress = onProgress,
                     )
                     visibilityState.targetState = false
                 },

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountViewModel.kt

@@ -923,6 +923,7 @@ class AccountViewModel(
         amountSats: Long,
         message: String,
         onError: (String, String, User?) -> Unit,
+        onProgress: (Float) -> Unit = {},
     ) = launchSigner {
         val recipient = baseNote.author?.pubkeyHex
         if (recipient == null) {
@@ -948,6 +949,7 @@ class AccountViewModel(
                 recipientPubKey = recipient,
                 zappedEvent = zappedEvent,
                 message = message,
+                onProgress = onProgress,
             )
             // No success toast — the kind:9321 round-trips through the
             // cache, attaches to the target Note via addNutzap, and the