feat: encrypted-history prompt, incoming-call alerts, message edit, panic button (v1.7.0+11)

P1 key_restore_prompt: offer recovery-key restore right after login
P2 incoming calls: mount overlay in app.dart + detect MSC3401 call.member
   (Element X signalling) — calls were previously invisible
P3 message edit: editMessage/EditMessage + Edit dialog (reactions/delete
   were already wired)
P5 panic button: new feature/panic module — hold-to-send alert text +
   m.location to a configured room; alert sent before geolocation so a
   denied permission never blocks it

All verified end-to-end in headless Chromium against production build.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/features/chat/presentation/chat_controller.dart

@@ -1,4 +1,4 @@
-// Version: 1.1.0 | Created: 2026-04-01
+// Version: 1.2.0 | Created: 2026-04-01 | Updated: 2026-07-04
 // Riverpod providers for chat timeline, send, upload, react, reply.
 
 import 'package:matrix/matrix.dart' show MatrixFile;
@@ -84,6 +84,27 @@ class SendReaction extends _$SendReaction {
   }
 }
 
+/// Edits an existing text message.
+@riverpod
+class EditMessage extends _$EditMessage {
+  @override
+  bool build() => false;
+
+  Future<String?> edit(String roomId, String eventId, String newText) async {
+    state = true;
+    try {
+      await ref
+          .read(chatRepositoryProvider)
+          .editMessage(roomId, eventId, newText);
+      return null;
+    } on Exception catch (e) {
+      return e.toString();
+    } finally {
+      state = false;
+    }
+  }
+}
+
 /// Deletes (redacts) a message by eventId.
 @riverpod
 class DeleteMessage extends _$DeleteMessage {