feat: migrate Firebase → NestJS REST API backend

Replace all Firebase SDK (Auth, Firestore, Storage) with HTTP calls
to backend.prosapp.co/api/v1:

- New ApiService singleton (JWT token, GET/POST/PATCH/DELETE/upload)
- auth_provider: Firebase Auth → /auth/login, /auth/register, /auth/phone/*
- services_provider + calendar_services_provider → /services endpoints
- professional_provider + professionals_provider → /professional-info, /users/professionals
- profile_form_provider + professional_form_provider → /users/me, /storage/upload
- cities/professions/settings providers → /cities, /professions, /settings
- firebase_chat_repository → polling via /chats endpoints (3s interval)
- firebase_score_repository → polling via /comments endpoints (10s interval)
- professional_detail_provider → /users/:id + /professional-info/:id
- dashboard_view: Firestore.add → POST /services
- chat_view + rating_view: FirebaseAuth.uid → AuthProvider.user.id
- Models: Timestamp → String for createdAt fields
- google_fonts upgraded to ^8.1.0 (Dart 3.12 compat)
- Remove firebase_core, firebase_auth, cloud_firestore, firebase_storage from pubspec

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

pubspec.lock

@@ -1,14 +1,6 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  _flutterfire_internals:
-    dependency: transitive
-    description:
-      name: _flutterfire_internals
-      sha256: a315d1c444402c3fa468de626d33a1c666041c87e9e195e8fb355b7084aefcc1
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.3.38"
   async:
     dependency: transitive
     description:
@@ -41,30 +33,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.2"
-  cloud_firestore:
-    dependency: "direct main"
-    description:
-      name: cloud_firestore
-      sha256: "1232370ad04c21c699d0e73b2dc2e1c3b49258f89a16f0119036fd3c6e8aa2f5"
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.0.2"
-  cloud_firestore_platform_interface:
-    dependency: transitive
-    description:
-      name: cloud_firestore_platform_interface
-      sha256: cfc64ae4a48bbb0ff6730b04f2d4653043c7a9b9008a991b1f2012a534b79e26
-      url: "https://pub.dev"
-    source: hosted
-    version: "6.2.8"
-  cloud_firestore_web:
-    dependency: transitive
-    description:
-      name: cloud_firestore_web
-      sha256: "3db4e4c10feae18d80da86982781578c8e76cb6a43cf83110d8d6a62af9a952a"
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.0.2"
   collection:
     dependency: transitive
     description:
@@ -169,78 +137,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.9.3+1"
-  firebase_auth:
-    dependency: "direct main"
-    description:
-      name: firebase_auth
-      sha256: "087fdcb54b0af6f4c5c756e1db4f90e9b65871b9b3a75fabaa0e0ee578301669"
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.1.1"
-  firebase_auth_platform_interface:
-    dependency: transitive
-    description:
-      name: firebase_auth_platform_interface
-      sha256: "8fac689f71ac3489a785579e99a4bad24a93ad3d78c313fb786ee517012d25f1"
-      url: "https://pub.dev"
-    source: hosted
-    version: "7.4.1"
-  firebase_auth_web:
-    dependency: transitive
-    description:
-      name: firebase_auth_web
-      sha256: "486b2527fcfcab01278378d8d4791f4f7bee8a9f15bf35e801ba08fbdd84c234"
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.12.3"
-  firebase_core:
-    dependency: "direct main"
-    description:
-      name: firebase_core
-      sha256: "1e06b0538ab3108a61d895ee16951670b491c4a94fce8f2d30e5de7a5eca4b28"
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.1.1"
-  firebase_core_platform_interface:
-    dependency: transitive
-    description:
-      name: firebase_core_platform_interface
-      sha256: "1003a5a03a61fc9a22ef49f37cbcb9e46c86313a7b2e7029b9390cf8c6fc32cb"
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.1.0"
-  firebase_core_web:
-    dependency: transitive
-    description:
-      name: firebase_core_web
-      sha256: "6643fe3dbd021e6ccfb751f7882b39df355708afbdeb4130fc50f9305a9d1a3d"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.17.2"
-  firebase_storage:
-    dependency: "direct main"
-    description:
-      name: firebase_storage
-      sha256: "01fdcef335d2c86a265e9eb3c5b3b489ddc5589e7fc18a74df84b31be9f0c15b"
-      url: "https://pub.dev"
-    source: hosted
-    version: "12.1.0"
-  firebase_storage_platform_interface:
-    dependency: transitive
-    description:
-      name: firebase_storage_platform_interface
-      sha256: "8fdbfc63af3441434f33a420a304a670b464ff71b8f12fccc80accba1378ca3b"
-      url: "https://pub.dev"
-    source: hosted
-    version: "5.1.25"
-  firebase_storage_web:
-    dependency: transitive
-    description:
-      name: firebase_storage_web
-      sha256: bb9a387ae26bf7358e118f191ee22167b30217cad551184592cc73e7f73bd470
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.9.10"
   fluro:
     dependency: "direct main"
     description: