Implement husband-wife connection dialogue and theme support for learn articles

lib/screens/settings/cycle_history_screen.dart

@@ -5,9 +5,16 @@ import 'package:collection/collection.dart';
 import '../../models/cycle_entry.dart';
 import '../../providers/user_provider.dart';
 
-class CycleHistoryScreen extends ConsumerWidget {
+class CycleHistoryScreen extends ConsumerStatefulWidget {
   const CycleHistoryScreen({super.key});
 
+  @override
+  ConsumerState<CycleHistoryScreen> createState() => _CycleHistoryScreenState();
+}
+
+class _CycleHistoryScreenState extends ConsumerState<CycleHistoryScreen> {
+  bool _isUnlocked = false;
+
   void _showDeleteAllDialog(BuildContext context, WidgetRef ref) {
     showDialog(
       context: context,
@@ -42,9 +49,85 @@ class CycleHistoryScreen extends ConsumerWidget {
     );
   }
 
+  Future<void> _authenticate() async {
+    final user = ref.read(userProfileProvider);
+    if (user?.privacyPin == null) return;
+
+    final controller = TextEditingController();
+    final pin = await showDialog<String>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Enter PIN'),
+        content: TextField(
+          controller: controller,
+          keyboardType: TextInputType.number,
+          obscureText: true,
+          maxLength: 4,
+          style: const TextStyle(fontSize: 24, letterSpacing: 8),
+          textAlign: TextAlign.center,
+          decoration: const InputDecoration(
+            hintText: '....',
+            border: OutlineInputBorder(),
+          ),
+          autofocus: true,
+        ),
+        actions: [
+          TextButton(onPressed: () => Navigator.pop(context), child: const Text('Cancel')),
+          ElevatedButton(
+            onPressed: () => Navigator.pop(context, controller.text),
+            child: const Text('Unlock'),
+          ),
+        ],
+      ),
+    );
+
+    if (pin == user!.privacyPin) {
+      setState(() {
+        _isUnlocked = true;
+      });
+    } else if (pin != null) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Incorrect PIN')),
+        );
+      }
+    }
+  }
+
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  Widget build(BuildContext context) {
     final entries = ref.watch(cycleEntriesProvider);
+    final user = ref.watch(userProfileProvider);
+    
+    // Privacy Check
+    final isProtected = user?.isHistoryProtected ?? false;
+    final hasPin = user?.privacyPin != null && user!.privacyPin!.isNotEmpty;
+    final isLocked = isProtected && hasPin && !_isUnlocked;
+
+    if (isLocked) {
+      return Scaffold(
+        appBar: AppBar(title: const Text('Cycle History')),
+        body: Center(
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              const Icon(Icons.lock_outline, size: 64, color: Colors.grey),
+              const SizedBox(height: 16),
+              const Text(
+                'History is Protected',
+                style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+              ),
+              const SizedBox(height: 24),
+              ElevatedButton.icon(
+                onPressed: _authenticate,
+                icon: const Icon(Icons.key),
+                label: const Text('Enter PIN to View'),
+              ),
+            ],
+          ),
+        ),
+      );
+    }
 
     final groupedEntries = groupBy(
       entries,