fix: merge old bookmarks into existing new bookmarks during migration

Instead of replacing the new bookmark list, the migration now checks for
an existing kind 10003 event and merges old bookmarks into it, skipping
duplicates that already exist.

https://claude.ai/code/session_01U9sjQHQMVVHxYiesoXjqop

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

@@ -1822,17 +1822,41 @@ class Account(
         if (!isWriteable()) return
 
         val oldList = oldBookmarkState.getBookmarkList() ?: return
-        val publicBookmarks = oldList.publicBookmarks()
-        val privateBookmarks = oldList.privateBookmarks(signer) ?: emptyList()
+        val oldPublic = oldList.publicBookmarks()
+        val oldPrivate = oldList.privateBookmarks(signer) ?: emptyList()
 
-        if (publicBookmarks.isEmpty() && privateBookmarks.isEmpty()) return
+        if (oldPublic.isEmpty() && oldPrivate.isEmpty()) return
+
+        val existingNewList = bookmarkState.getBookmarkList()
 
         val newEvent =
-            BookmarkListEvent.create(
-                publicBookmarks = publicBookmarks,
-                privateBookmarks = privateBookmarks,
-                signer = signer,
-            )
+            if (existingNewList != null) {
+                val existingPublic = existingNewList.publicBookmarks()
+                val existingPrivate = existingNewList.privateBookmarks(signer) ?: emptyList()
+
+                val existingPublicIds = existingPublic.map { it.toTagIdOnly().toList() }.toSet()
+                val existingPrivateIds = existingPrivate.map { it.toTagIdOnly().toList() }.toSet()
+
+                val newPublic = oldPublic.filter { it.toTagIdOnly().toList() !in existingPublicIds }
+                val newPrivate = oldPrivate.filter { it.toTagIdOnly().toList() !in existingPrivateIds }
+
+                if (newPublic.isEmpty() && newPrivate.isEmpty()) return
+
+                val mergedPublic = existingPublic + newPublic
+                val mergedPrivate = existingPrivate + newPrivate
+
+                BookmarkListEvent.create(
+                    publicBookmarks = mergedPublic,
+                    privateBookmarks = mergedPrivate,
+                    signer = signer,
+                )
+            } else {
+                BookmarkListEvent.create(
+                    publicBookmarks = oldPublic,
+                    privateBookmarks = oldPrivate,
+                    signer = signer,
+                )
+            }
 
         sendMyPublicAndPrivateOutbox(newEvent)
     }

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

@@ -581,7 +581,6 @@ object LocalCache : ILocalCache, ICacheProvider {
         return false
     }
 
-
     fun consumeRegularEvent(
         event: Event,
         relay: NormalizedRelayUrl?,