feat(#174): promote name-only block to pubkey (advert/DM) + 30d age-out

BlockService.maybePromote(name,key): when a name-only block links to a pubkey,
add the key to blockedKeys and drop the name entry. Connector calls it on every
contact advert AND incoming DM (the two ways we learn a name<->key link).
_pruneExpiredNames on load drops name-only blocks older than 30 days.

Epic A #165 / A7 #174. Design: docs/architecture/block-contract-as-built.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/connector/meshcore_connector.dart

@@ -4797,6 +4797,12 @@ class MeshCoreConnector extends ChangeNotifier {
       return;
     }
 
+    // Learned name<->key from this advert: promote a matching name-only block.
+    final blockService = _blockService;
+    if (blockService != null) {
+      unawaited(blockService.maybePromote(contact.name, contact.publicKeyHex));
+    }
+
     if (contact.type == advTypeRepeater) {
       final removedCount = _contactUnreadCount[contact.publicKeyHex] ?? 0;
       _cachedContactsUnreadTotal = (_cachedContactsUnreadTotal - removedCount)
@@ -5051,6 +5057,15 @@ class MeshCoreConnector extends ChangeNotifier {
       if (contact != null) {
         _updateContactLastMessageAt(contact.publicKeyHex, message.timestamp);
       }
+      if (contact != null) {
+        // Learned name<->key from this DM: promote a matching name-only block.
+        final blockService = _blockService;
+        if (blockService != null) {
+          unawaited(
+            blockService.maybePromote(contact.name, contact.publicKeyHex),
+          );
+        }
+      }
       if (!message.isOutgoing) {
         final existing = _conversations[message.senderKeyHex];
         final incomingTimestamp = message.timestamp.millisecondsSinceEpoch;

lib/services/block_service.dart

@@ -24,6 +24,7 @@ class BlockService extends ChangeNotifier {
     _blockedNames
       ..clear()
       ..addAll(await _store.loadNames());
+    await _pruneExpiredNames();
     notifyListeners();
   }
 
@@ -61,4 +62,35 @@ class BlockService extends ChangeNotifier {
     await _store.saveNames(_blockedNames);
     notifyListeners();
   }
+
+  /// Name-only blocks older than this are pruned on load (self-cleaning).
+  static const Duration _nameBlockTtl = Duration(days: 30);
+
+  /// Promote a name-only block to a durable pubkey block once we learn the
+  /// identity behind it (observed via an advert or a DM). No-op if the name
+  /// isn't name-blocked.
+  Future<void> maybePromote(String name, String publicKeyHex) async {
+    final n = name.trim().toLowerCase();
+    if (n.isEmpty || !_blockedNames.containsKey(n)) return;
+    _blockedNames.remove(n);
+    _blockedKeys.add(publicKeyHex.toLowerCase());
+    await _store.saveNames(_blockedNames);
+    await _store.saveKeys(_blockedKeys);
+    notifyListeners();
+  }
+
+  /// Drop name-only blocks that never linked to a pubkey within [_nameBlockTtl].
+  Future<void> _pruneExpiredNames() async {
+    final cutoff =
+        DateTime.now().millisecondsSinceEpoch - _nameBlockTtl.inMilliseconds;
+    final expired = _blockedNames.entries
+        .where((e) => e.value < cutoff)
+        .map((e) => e.key)
+        .toList();
+    if (expired.isEmpty) return;
+    for (final n in expired) {
+      _blockedNames.remove(n);
+    }
+    await _store.saveNames(_blockedNames);
+  }
 }