test(search): stop the date tests asserting UTC when the parser means local

Six tests failed on any machine outside UTC, by exactly that machine's offset:

  QueryParserTest     sinceDate, sinceDateYearOnly, combinedQuery
  QuerySerializerTest sinceDate, untilDate, combinedQuery

They hardcoded 1735689600L -- 2025-01-01 midnight *UTC* -- but the parser now
returns the reader's own midnight, and the serializer formats through
`DateUtils.localDay`. In America/New_York the parser answered 1735707600 and the
serializer rendered "2024-12-31", both correct. The production code is right; the
assertions were left behind when the bound became local.

The same file already had it right further down, where the newer cases assert
`LocalClock.startOfDay(SearchDate(...))` under a comment explaining that a bound
is the reader's midnight and not UTC's. These six now say the same thing, so they
state the intended behaviour rather than the behaviour of a UTC build machine.

`timestampToDate2025` keeps its UTC literal deliberately: `timestampToDate` is
plain epoch arithmetic in `DateUtils`, not the local formatter `serialize` uses.
Changing it would have broken a passing test -- the two paths in `QuerySerializer`
genuinely differ.

Verified green in America/New_York, UTC, Pacific/Auckland and Asia/Kolkata --
37 + 19 tests, zero failures in each. Full quartz, commons and amethyst suites
pass locally, which they did not before this.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wwk8tDEaEvsNoGbtrjZavz

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/search/QueryParserTest.kt

@@ -101,15 +101,13 @@ class QueryParserTest {
     @Test
     fun sinceDate() {
         val q = QueryParser.parse("since:2025-01-01")
-        // 2025-01-01 00:00:00 UTC
-        assertEquals(1735689600L, q.since)
+        assertEquals(LocalClock.startOfDay(SearchDate(2025, 1, 1)), q.since)
     }
 
     @Test
     fun sinceDateYearOnly() {
         val q = QueryParser.parse("since:2025")
-        // 2025-01-01 00:00:00 UTC
-        assertEquals(1735689600L, q.since)
+        assertEquals(LocalClock.startOfDay(SearchDate(2025, 1, 1)), q.since)
     }
 
     @Test
@@ -214,7 +212,7 @@ class QueryParserTest {
     fun combinedQuery() {
         val q = QueryParser.parse("kind:note since:2025-01-01 #bitcoin -spam lightning")
         assertEquals(listOf(1), q.kinds.toList())
-        assertEquals(1735689600L, q.since)
+        assertEquals(LocalClock.startOfDay(SearchDate(2025, 1, 1)), q.since)
         assertEquals(listOf("bitcoin"), q.hashtags.toList())
         assertEquals(listOf("spam"), q.excludeTerms.toList())
         assertEquals("lightning", q.text)

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/search/QuerySerializerTest.kt

@@ -20,6 +20,8 @@
  */
 package com.vitorpamplona.amethyst.commons.search
 
+import com.vitorpamplona.amethyst.commons.search.calendar.LocalClock
+import com.vitorpamplona.amethyst.commons.search.calendar.SearchDate
 import kotlinx.collections.immutable.persistentListOf
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -63,13 +65,13 @@ class QuerySerializerTest {
 
     @Test
     fun sinceDate() {
-        val q = SearchQuery(since = 1735689600L) // 2025-01-01
+        val q = SearchQuery(since = LocalClock.startOfDay(SearchDate(2025, 1, 1)))
         assertEquals("since:2025-01-01", QuerySerializer.serialize(q))
     }
 
     @Test
     fun untilDate() {
-        val q = SearchQuery(until = 1735689600L)
+        val q = SearchQuery(until = LocalClock.startOfDay(SearchDate(2025, 1, 1)))
         assertEquals("until:2025-01-01", QuerySerializer.serialize(q))
     }
 
@@ -115,7 +117,7 @@ class QuerySerializerTest {
             SearchQuery(
                 authorNames = persistentListOf("vitor"),
                 kinds = persistentListOf(1),
-                since = 1735689600L,
+                since = LocalClock.startOfDay(SearchDate(2025, 1, 1)),
                 hashtags = persistentListOf("bitcoin"),
                 text = "lightning",
                 excludeTerms = persistentListOf("spam"),