feat(i18n): localize settings + search screens

Extend the en/zh localization to the two screens reached from the home
app bar (the "全都用 + 多语言" ask):
- settings: title, theme-mode segments (System/Light/Dark), seed-color
  description, color-picker + clear-data dialogs.
- search: hint, error, empty/no-results states, Notes/Documents section
  headers, page label.

New ARB keys regenerated; l10n_test now asserts the new keys resolve in
both English and Chinese.

flutter analyze: 0 issues. l10n_test: 3/3.

lib/screens/search_screen.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../l10n/app_localizations.dart';
 import '../models/note.dart';
 import '../providers/search_provider.dart';
 import 'note_editor_screen.dart';
@@ -42,16 +43,17 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
   @override
   Widget build(BuildContext context) {
     final results = ref.watch(searchResultsProvider);
+    final l = AppLocalizations.of(context);
 
     return Scaffold(
       appBar: AppBar(
         title: TextField(
           controller: _controller,
           autofocus: true,
-          decoration: const InputDecoration(
-            hintText: 'Search notes and documents...',
+          decoration: InputDecoration(
+            hintText: l.searchHint,
             border: InputBorder.none,
-            hintStyle: TextStyle(color: Colors.grey),
+            hintStyle: const TextStyle(color: Colors.grey),
           ),
           onChanged: _onQueryChanged,
           onSubmitted: (value) {
@@ -72,14 +74,14 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
       ),
       body: results.when(
         loading: () => const Center(child: CircularProgressIndicator()),
-        error: (e, _) => Center(child: Text('Search error: $e')),
+        error: (e, _) => Center(child: Text(l.searchError('$e'))),
         data: (hits) {
           final query = ref.watch(searchQueryProvider);
           if (query.isEmpty) {
-            return const Center(
+            return Center(
               child: Text(
-                'Type to search your notes and documents',
-                style: TextStyle(color: Colors.grey),
+                l.typeToSearch,
+                style: const TextStyle(color: Colors.grey),
               ),
             );
           }
@@ -95,7 +97,7 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
                   ),
                   const SizedBox(height: 16),
                   Text(
-                    'No results for "$query"',
+                    l.noResultsFor(query),
                     style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                       color: Theme.of(context).colorScheme.onSurfaceVariant,
                     ),
@@ -114,7 +116,7 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
                 Padding(
                   padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
                   child: Text(
-                    'Notes',
+                    l.sectionNotes,
                     style: Theme.of(context).textTheme.titleSmall?.copyWith(
                       fontWeight: FontWeight.bold,
                       color: Theme.of(context).colorScheme.primary,
@@ -129,7 +131,7 @@ class _SearchScreenState extends ConsumerState<SearchScreen> {
                 Padding(
                   padding: const EdgeInsets.fromLTRB(16, 16, 16, 4),
                   child: Text(
-                    'Documents',
+                    l.sectionDocuments,
                     style: Theme.of(context).textTheme.titleSmall?.copyWith(
                       fontWeight: FontWeight.bold,
                       color: Theme.of(context).colorScheme.primary,
@@ -209,7 +211,7 @@ class _DocumentSearchResultTile extends StatelessWidget {
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
           Text(
-            'Page ${pageNumber + 1}',
+            AppLocalizations.of(context).pageLabel(pageNumber + 1),
             style: Theme.of(context).textTheme.bodySmall,
           ),
           if (snippet.isNotEmpty)

lib/screens/settings_screen.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_colorpicker/flutter_colorpicker.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../l10n/app_localizations.dart';
 import '../models/pen_tool.dart';
 import '../models/pressure_curve.dart';
 import '../providers/settings_provider.dart';
@@ -20,8 +21,9 @@ class SettingsScreen extends ConsumerWidget {
     showDialog(
       context: context,
       builder: (context) {
+        final l = AppLocalizations.of(context);
         return AlertDialog(
-          title: const Text('Pick a color'),
+          title: Text(l.pickColor),
           content: SingleChildScrollView(
             child: ColorPicker(
               pickerColor: pickerColor,
@@ -31,14 +33,14 @@ class SettingsScreen extends ConsumerWidget {
           actions: [
             TextButton(
               onPressed: () => Navigator.of(context).pop(),
-              child: const Text('Cancel'),
+              child: Text(l.cancel),
             ),
             TextButton(
               onPressed: () {
                 onPicked(pickerColor);
                 Navigator.of(context).pop();
               },
-              child: const Text('OK'),
+              child: Text(l.ok),
             ),
           ],
         );
@@ -50,7 +52,7 @@ class SettingsScreen extends ConsumerWidget {
     showDialog(
       context: context,
       builder: (ctx) => AlertDialog(
-        title: const Text('Clear all local settings?'),
+        title: Text(AppLocalizations.of(ctx).clearSettingsTitle),
         content: const Text(
           'This will reset pen defaults and appearance settings. '
           'Notes and documents are not affected.',
@@ -58,17 +60,18 @@ class SettingsScreen extends ConsumerWidget {
         actions: [
           TextButton(
             onPressed: () => Navigator.pop(ctx),
-            child: const Text('Cancel'),
+            child: Text(AppLocalizations.of(ctx).cancel),
           ),
           TextButton(
             onPressed: () {
               ref.read(settingsProvider).clearAllData();
               Navigator.pop(ctx);
               ScaffoldMessenger.of(context).showSnackBar(
-                const SnackBar(content: Text('Settings reset to defaults')),
+                SnackBar(
+                    content: Text(AppLocalizations.of(context).settingsReset)),
               );
             },
-            child: const Text('Clear'),
+            child: Text(AppLocalizations.of(ctx).clear),
           ),
         ],
       ),
@@ -81,7 +84,7 @@ class SettingsScreen extends ConsumerWidget {
     final colorScheme = Theme.of(context).colorScheme;
 
     return Scaffold(
-      appBar: AppBar(title: const Text('Settings')),
+      appBar: AppBar(title: Text(AppLocalizations.of(context).settings)),
       body: ListView(
         children: [
           _SectionHeader(title: 'Defaults', icon: Icons.tune),
@@ -221,21 +224,21 @@ class SettingsScreen extends ConsumerWidget {
                 ),
                 const SizedBox(height: 4),
                 SegmentedButton<ThemeMode>(
-                  segments: const [
+                  segments: [
                     ButtonSegment(
                       value: ThemeMode.system,
-                      label: Text('System'),
-                      icon: Icon(Icons.brightness_auto),
+                      label: Text(AppLocalizations.of(context).themeSystem),
+                      icon: const Icon(Icons.brightness_auto),
                     ),
                     ButtonSegment(
                       value: ThemeMode.light,
-                      label: Text('Light'),
-                      icon: Icon(Icons.light_mode),
+                      label: Text(AppLocalizations.of(context).themeLight),
+                      icon: const Icon(Icons.light_mode),
                     ),
                     ButtonSegment(
                       value: ThemeMode.dark,
-                      label: Text('Dark'),
-                      icon: Icon(Icons.dark_mode),
+                      label: Text(AppLocalizations.of(context).themeDark),
+                      icon: const Icon(Icons.dark_mode),
                     ),
                   ],
                   selected: {settings.themeMode},
@@ -272,7 +275,7 @@ class SettingsScreen extends ConsumerWidget {
                       ),
                     ),
                     const SizedBox(width: 12),
-                    const Text('Seed color for Material 3 theme'),
+                    Text(AppLocalizations.of(context).seedColorDesc),
                   ],
                 ),
               ],