feat: Phase 1 critical gaps — gamification API, Razorpay checkout, Google OAuth, notifications

- Fix gamification endpoints to use Node.js server (app.eventifyplus.com)
- Replace 6 mock gamification methods with real API calls (dashboard, leaderboard, shop, redeem, submit)
- Add booking models, service, payment service (Razorpay), checkout provider
- Add 3-step CheckoutScreen with Razorpay native modal integration
- Add Google OAuth login (Flutter + Django backend)
- Add full notifications system (Django model + 3 endpoints + Flutter UI)
- Register CheckoutProvider, NotificationProvider in main.dart MultiProvider
- Wire notification bell in HomeScreen app bar
- Add razorpay_flutter ^1.3.7 and google_sign_in ^6.2.2 packages

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pubspec.lock

@@ -137,6 +137,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.8"
+  eventify:
+    dependency: transitive
+    description:
+      name: eventify
+      sha256: b829429f08586cc2001c628e7499e3e3c2493a1d895fd73b00ecb23351aa5a66
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.1"
   fake_async:
     dependency: transitive
     description:
@@ -336,6 +344,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.1.3"
+  google_identity_services_web:
+    dependency: transitive
+    description:
+      name: google_identity_services_web
+      sha256: "5d187c46dc59e02646e10fe82665fc3884a9b71bc1c90c2b8b749316d33ee454"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.3.3+1"
   google_maps:
     dependency: transitive
     description:
@@ -384,6 +400,46 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.5.14+3"
+  google_sign_in:
+    dependency: "direct main"
+    description:
+      name: google_sign_in
+      sha256: d0a2c3bcb06e607bb11e4daca48bd4b6120f0bbc4015ccebbe757d24ea60ed2a
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.3.0"
+  google_sign_in_android:
+    dependency: transitive
+    description:
+      name: google_sign_in_android
+      sha256: d5e23c56a4b84b6427552f1cf3f98f716db3b1d1a647f16b96dbb5b93afa2805
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.2.1"
+  google_sign_in_ios:
+    dependency: transitive
+    description:
+      name: google_sign_in_ios
+      sha256: "102005f498ce18442e7158f6791033bbc15ad2dcc0afa4cf4752e2722a516c96"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.9.0"
+  google_sign_in_platform_interface:
+    dependency: transitive
+    description:
+      name: google_sign_in_platform_interface
+      sha256: "5f6f79cf139c197261adb6ac024577518ae48fdff8e53205c5373b5f6430a8aa"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.5.0"
+  google_sign_in_web:
+    dependency: transitive
+    description:
+      name: google_sign_in_web
+      sha256: "460547beb4962b7623ac0fb8122d6b8268c951cf0b646dd150d60498430e4ded"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.12.4+4"
   html:
     dependency: transitive
     description:
@@ -393,7 +449,7 @@ packages:
     source: hosted
     version: "0.15.6"
   http:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: http
       sha256: bb2ce4590bc2667c96f318d68cac1b5a7987ec819351d32b1c987239a815e007
@@ -672,6 +728,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.1.5+1"
+  razorpay_flutter:
+    dependency: "direct main"
+    description:
+      name: razorpay_flutter
+      sha256: "8d985b769808cb6c8d3f2fbcc25f9ab78e29191965c31c98e2d69d55d9d20ff1"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.4.3"
   rxdart:
     dependency: transitive
     description: