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/panic/presentation/panic_button.dart

@@ -0,0 +1,70 @@
+// Version: 1.0.0 | Created: 2026-07-04
+// Panic trigger button for the rooms AppBar. Push-to-talk style:
+// HOLD to fire the alert; a plain tap only shows the hint. Only rendered
+// when a panic configuration exists in account data.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../data/panic_repository.dart';
+
+class PanicButton extends ConsumerStatefulWidget {
+  const PanicButton({super.key});
+
+  @override
+  ConsumerState<PanicButton> createState() => _PanicButtonState();
+}
+
+class _PanicButtonState extends ConsumerState<PanicButton> {
+  bool _sending = false;
+
+  Future<void> _trigger() async {
+    if (_sending) return;
+    setState(() => _sending = true);
+    final messenger = ScaffoldMessenger.of(context);
+    messenger.showSnackBar(
+      const SnackBar(content: Text('Sending emergency alert…')),
+    );
+    final error = await ref.read(panicRepositoryProvider).trigger();
+    if (!mounted) return;
+    setState(() => _sending = false);
+    messenger.hideCurrentSnackBar();
+    messenger.showSnackBar(
+      SnackBar(
+        backgroundColor: error == null ? Colors.green.shade800 : null,
+        content: Text(
+          error ?? 'Emergency alert sent with your location.',
+        ),
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // Hide when not configured. Config lives in account data, which is
+    // available once sync has run; rebuilds happen with the parent screen.
+    final configured = ref.watch(panicRepositoryProvider).config != null;
+    if (!configured) return const SizedBox.shrink();
+
+    return GestureDetector(
+      onLongPress: _trigger,
+      child: IconButton(
+        tooltip: 'Hold to send emergency alert',
+        icon: _sending
+            ? const SizedBox(
+                width: 20,
+                height: 20,
+                child: CircularProgressIndicator(strokeWidth: 2),
+              )
+            : const Icon(Icons.emergency_share, color: Colors.red),
+        onPressed: () {
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(
+              content: Text('Hold the button to send the emergency alert.'),
+            ),
+          );
+        },
+      ),
+    );
+  }
+}