fix(reply): cache FlutterView to prevent crash on screen re-open

View.of(context) was being called in didChangeMetrics() during widget
deactivation, causing "Looking up a deactivated widget's ancestor"
errors. The context becomes invalid before mounted becomes false.

Fixed by caching the FlutterView reference in didChangeDependencies()
for both _ReplyScreenState and _ReplyToolbarState, then using the
cached reference in didChangeMetrics().

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

lib/screens/compose/reply_screen.dart

···
 import 'dart:async';
 import 'dart:math' as math;
+import 'dart:ui' show FlutterView;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
···
   bool _authInvalidated = false;
   double _lastKeyboardHeight = 0;
   Timer? _bannerDismissTimer;
+  FlutterView? _cachedView;
 
   @override
   void initState() {
···
     });
   }
 
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    // Cache the view reference so we can safely use it in didChangeMetrics
+    // even when the widget is being deactivated
+    _cachedView = View.of(context);
+  }
+
   void _setupAuthListener() {
     try {
       context.read<AuthProvider>().addListener(_onAuthChanged);
···
     super.didChangeMetrics();
     // Guard against being called after widget is deactivated
     // (can happen during keyboard animation while navigating away)
-    if (!mounted) return;
+    if (!mounted || _cachedView == null) return;
 
-    final keyboardHeight = View.of(context).viewInsets.bottom;
+    final keyboardHeight = _cachedView!.viewInsets.bottom;
 
     // Detect keyboard closing and unfocus text field
     if (_lastKeyboardHeight > 0 && keyboardHeight == 0) {
···
     with WidgetsBindingObserver {
   final ValueNotifier<double> _keyboardMarginNotifier = ValueNotifier(0);
   final ValueNotifier<double> _safeAreaBottomNotifier = ValueNotifier(0);
+  FlutterView? _cachedView;
 
   @override
   void initState() {
···
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
+    // Cache view reference for safe access in didChangeMetrics
+    _cachedView = View.of(context);
     _updateMargins();
   }
 
···
 
   @override
   void didChangeMetrics() {
-    _updateMargins();
+    // Schedule update after frame to ensure context is valid
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      _updateMargins();
+    });
   }
 
   void _updateMargins() {
-    if (!mounted) {
+    if (!mounted || _cachedView == null) {
       return;
     }
-    final view = View.of(context);
+    final view = _cachedView!;
     final devicePixelRatio = view.devicePixelRatio;
     final keyboardInset = view.viewInsets.bottom / devicePixelRatio;
     final viewPaddingBottom = view.viewPadding.bottom / devicePixelRatio;