feat: Phase 6 — Marmot account integration & event routing

Wire Marmot MLS group messaging into the app's Account lifecycle,
event processing pipeline, and relay subscription system.

New files:
- AndroidMlsGroupStateStore: encrypted file-based MLS state storage
  using KeyStoreEncryption (AES/GCM backed by Android KeyStore)
- MarmotManager: central coordinator holding all Marmot components
  (MlsGroupManager, KeyPackageRotationManager, subscription/inbound/
  outbound processors, WelcomeSender)
- MarmotGroupEventsEoseManager: relay subscription manager for
  kind:445 GroupEvent filters via AccountFilterAssembler

Account integration:
- MarmotManager initialized during Account startup with restoreAll()
- Outbound methods: sendMarmotGroupMessage, addMarmotGroupMember,
  publishMarmotKeyPackage(s), createMarmotGroup
- GroupEvent (kind:445) and KeyPackageEvent (kind:30443) added to
  LocalCache.justConsumeInnerInner() dispatch

Event routing:
- GroupEventHandler: processes inbound kind:445 events through
  MarmotInboundProcessor, indexes decrypted inner events in LocalCache
- GiftWrapEventHandler extended: detects kind:444 WelcomeEvent after
  NIP-59 unwrap, routes to MarmotManager.processWelcome(), triggers
  KeyPackage rotation when needed
- WelcomeEvent enhanced with optional "h" tag for group ID routing

https://claude.ai/code/session_01W2LHazEt4E3W4hn8f7gWVW

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/MarmotWelcomeSender.kt

@@ -71,6 +71,7 @@ class MarmotWelcomeSender(
         recipientPubKey: HexKey,
         keyPackageEventId: HexKey,
         relays: List<NormalizedRelayUrl>,
+        nostrGroupId: HexKey? = null,
     ): WelcomeDelivery? {
         val welcomeBytes = commitResult.welcomeBytes ?: return null
 
@@ -83,6 +84,7 @@ class MarmotWelcomeSender(
                 relays = relays,
                 recipientPubKey = recipientPubKey,
                 signer = signer,
+                nostrGroupId = nostrGroupId,
             )
 
         return WelcomeDelivery(
@@ -109,6 +111,7 @@ class MarmotWelcomeSender(
         recipientPubKey: HexKey,
         keyPackageEventId: HexKey,
         relays: List<NormalizedRelayUrl>,
+        nostrGroupId: HexKey? = null,
     ): WelcomeDelivery {
         val welcomeBase64 = Base64.encode(welcomeBytes)
 
@@ -119,6 +122,7 @@ class MarmotWelcomeSender(
                 relays = relays,
                 recipientPubKey = recipientPubKey,
                 signer = signer,
+                nostrGroupId = nostrGroupId,
             )
 
         return WelcomeDelivery(

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mip02Welcome/WelcomeEvent.kt

@@ -67,6 +67,12 @@ class WelcomeEvent(
     /** Content encoding (must be "base64") */
     fun encoding() = tags.welcomeEncoding()
 
+    /** Nostr group ID from the "h" tag (for recipient to identify the group) */
+    fun nostrGroupId(): HexKey? =
+        tags.firstNotNullOfOrNull { tag ->
+            if (tag.size >= 2 && tag[0] == "h") tag[1] else null
+        }
+
     override fun isContentEncoded() = true
 
     companion object {
@@ -77,12 +83,14 @@ class WelcomeEvent(
             welcomeBase64: String,
             keyPackageEventId: HexKey,
             relays: List<NormalizedRelayUrl>,
+            nostrGroupId: HexKey? = null,
             createdAt: Long = TimeUtils.now(),
             initializer: TagArrayBuilder<WelcomeEvent>.() -> Unit = {},
         ) = eventTemplate(KIND, welcomeBase64, createdAt) {
             keyPackageEventId(keyPackageEventId)
             welcomeRelays(relays)
             encoding()
+            nostrGroupId?.let { addUnique(arrayOf("h", it)) }
             initializer()
         }
     }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mip02Welcome/WelcomeGiftWrap.kt

@@ -57,6 +57,7 @@ object WelcomeGiftWrap {
         relays: List<NormalizedRelayUrl>,
         recipientPubKey: HexKey,
         signer: NostrSigner,
+        nostrGroupId: HexKey? = null,
         createdAt: Long = TimeUtils.now(),
     ): GiftWrapEvent {
         // Step 1: Build the WelcomeEvent template and sign it
@@ -65,6 +66,7 @@ object WelcomeGiftWrap {
                 welcomeBase64 = welcomeBase64,
                 keyPackageEventId = keyPackageEventId,
                 relays = relays,
+                nostrGroupId = nostrGroupId,
                 createdAt = createdAt,
             )
         val welcomeEvent: WelcomeEvent = signer.sign(welcomeTemplate)