feat: Phase 2 — 11 high-priority gaps implemented across home, auth, gamification, profile, and event detail

Phase 2 gaps completed:
- HOME-001: Hero slider pause-on-touch (GestureDetector wraps PageView)
- HOME-003: Calendar bottom sheet with TableCalendar (replaces custom dialog)
- AUTH-004: District dropdown on signup (14 Kerala districts)
- EVT-003: Mobile sticky "Book Now" bar + desktop CTA wired to CheckoutScreen
- ACH-001: Real achievements from dashboard API with fallback defaults
- GAM-002: 3-card EP row (Lifetime EP / Liquid EP / Reward Points)
- GAM-005: Horizontal tier roadmap Bronze→Silver→Gold→Platinum→Diamond
- CTR-001: Submission status chips (PENDING/APPROVED/REJECTED)
- CTR-002: +EP badge on approved submissions
- PROF-003: Gamification cards on profile screen with Consumer<GamificationProvider>
- UX-001: Shimmer skeleton loaders (shimmer ^3.0.0) replacing CircularProgressIndicator

Already complete (verified, no changes needed):
- HOME-002: Category shelves already built in _buildTypeSection()
- LDR-002: Podium visualization already built (_buildPodium / _buildDesktopPodium)
- BOOK-004: UPI handled natively by Razorpay SDK

Deferred: LOC-001/002 (needs Django haversine endpoint)
Skipped: AUTH-002 (OTP needs SMS provider decision)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/screens/login_screen.dart

@@ -595,6 +595,13 @@ class _RegisterScreenState extends State<RegisterScreen> {
   final AuthService _auth = AuthService();
 
   bool _loading = false;
+  String? _selectedDistrict;
+
+  static const _districts = [
+    'Thiruvananthapuram', 'Kollam', 'Pathanamthitta', 'Alappuzha',
+    'Kottayam', 'Idukki', 'Ernakulam', 'Thrissur', 'Palakkad',
+    'Malappuram', 'Kozhikode', 'Wayanad', 'Kannur', 'Kasaragod',
+  ];
 
   @override
   void dispose() {
@@ -625,6 +632,7 @@ class _RegisterScreenState extends State<RegisterScreen> {
         email: email,
         phoneNumber: phone,
         password: pass,
+        district: _selectedDistrict,
       );
 
       if (!mounted) return;
@@ -679,6 +687,13 @@ class _RegisterScreenState extends State<RegisterScreen> {
                         const SizedBox(height: 8),
                         TextFormField(controller: _phoneCtrl, decoration: const InputDecoration(labelText: 'Phone'), validator: _phoneValidator, keyboardType: TextInputType.phone),
                         const SizedBox(height: 8),
+                        DropdownButtonFormField<String>(
+                          value: _selectedDistrict,
+                          decoration: const InputDecoration(labelText: 'District (optional)'),
+                          items: _districts.map((d) => DropdownMenuItem(value: d, child: Text(d))).toList(),
+                          onChanged: (v) => setState(() => _selectedDistrict = v),
+                        ),
+                        const SizedBox(height: 8),
                         TextFormField(controller: _passCtrl, obscureText: true, decoration: const InputDecoration(labelText: 'Password'), validator: _passwordValidator),
                         const SizedBox(height: 8),
                         TextFormField(controller: _confirmCtrl, obscureText: true, decoration: const InputDecoration(labelText: 'Confirm password'), validator: _passwordValidator),