feat: Phase 3 — 26 medium-priority gaps implemented

P3-A/K  Profile: Eventify ID glassmorphic badge (tap-to-copy), DiceBear
        Notionists avatar via TierAvatarRing, district picker (14 pills)
        with 183-day cooldown lock, multipart photo upload to server
P3-B    Home: Top Events converted to PageView scroll-snap
        (viewportFraction 0.9 + PageScrollPhysics)
P3-C    Event detail: contributor widget (tier ring + name + navigation),
        related events horizontal row; added getEventsByCategory() to
        EventsService; added contributorId/Name/Tier fields to EventModel
P3-D    Kerala pincodes: 463-entry JSON (all 14 districts), registered as
        asset, async-loaded in SearchScreen replacing hardcoded 32 cities
P3-E    Checkout: promo code field + Apply/Remove button in Step 2,
        discountAmount subtracted from total, applyPromo()/resetPromo()
        methods in CheckoutProvider
P3-F/G  Gamification: reward cycle countdown + EP→RP progress bar (blue→
        amber) in contribute + profile screens; TierAvatarRing in podium
        and all leaderboard rows; GlassCard current-user stats card at
        top of leaderboard tab
P3-H    New ContributorProfileScreen: tier ring, stats, submission grid
        with status chips; getDashboardForUser() in GamificationService;
        wired from leaderboard row taps
P3-I    Achievements: 11 default badges (up from 6), 6 new icon map
        entries; progress % labels already confirmed present
P3-J    Reviews: CustomPainter circular arc rating ring (amber, 84px)
        replaces large rating number in ReviewSummary
P3-L    Share rank card: RepaintBoundary → PNG capture → Share.shareXFiles;
        share button wired in profile header and leaderboard tab
P3-M    SafeArea audit: home bottom nav, contribute/achievements scroll
        padding, profile CustomScrollView top inset

New files: tier_avatar_ring.dart, glass_card.dart,
  eventify_bottom_sheet.dart, contributor_profile_screen.dart,
  share_rank_card.dart, assets/data/kerala_pincodes.json
New dep:   path_provider ^2.1.0

lib/widgets/eventify_bottom_sheet.dart

@@ -0,0 +1,96 @@
+import 'package:flutter/material.dart';
+
+void showEventifyBottomSheet(
+  BuildContext context, {
+  required String title,
+  required Widget child,
+  double initialSize = 0.5,
+  double minSize = 0.3,
+  double maxSize = 0.9,
+  bool isDismissible = true,
+}) {
+  showModalBottomSheet(
+    context: context,
+    isScrollControlled: true,
+    isDismissible: isDismissible,
+    backgroundColor: Colors.transparent,
+    builder: (_) => DraggableScrollableSheet(
+      initialChildSize: initialSize,
+      minChildSize: minSize,
+      maxChildSize: maxSize,
+      expand: false,
+      builder: (_, scrollController) => _EventifyBottomSheetContent(
+        title: title,
+        child: child,
+        scrollController: scrollController,
+      ),
+    ),
+  );
+}
+
+class _EventifyBottomSheetContent extends StatelessWidget {
+  const _EventifyBottomSheetContent({
+    required this.title,
+    required this.child,
+    required this.scrollController,
+  });
+
+  final String title;
+  final Widget child;
+  final ScrollController scrollController;
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      decoration: const BoxDecoration(
+        color: Color(0xFF0F172A),
+        borderRadius: BorderRadius.vertical(top: Radius.circular(20)),
+      ),
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          const SizedBox(height: 12),
+          Center(
+            child: Container(
+              width: 40,
+              height: 4,
+              decoration: BoxDecoration(
+                color: Colors.white24,
+                borderRadius: BorderRadius.circular(2),
+              ),
+            ),
+          ),
+          const SizedBox(height: 8),
+          Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16),
+            child: Row(
+              children: [
+                Expanded(
+                  child: Text(
+                    title,
+                    style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                          fontWeight: FontWeight.w600,
+                          color: Colors.white,
+                        ),
+                  ),
+                ),
+                IconButton(
+                  icon: const Icon(Icons.close, color: Colors.white54),
+                  onPressed: () => Navigator.pop(context),
+                ),
+              ],
+            ),
+          ),
+          const Divider(color: Colors.white12, height: 1),
+          Expanded(
+            child: SingleChildScrollView(
+              controller: scrollController,
+              child: child,
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}