feat: Add expense management features with tabs for expenses, balances, and settlements

- Implemented ExpensesTab to display a list of expenses with details.
- Created GroupExpensesPage to manage group expenses with a tabbed interface.
- Added SettlementsTab to show optimized settlements between users.
- Developed data models for Expense and Balance, including necessary methods for serialization.
- Introduced CountRepository for Firestore interactions related to expenses.
- Added CountService to handle business logic for expenses and settlements.
- Integrated image picker for receipt uploads.
- Updated main.dart to include CountBloc and CountRepository.
- Enhanced pubspec.yaml with new dependencies for image picking and Firebase storage.

Not Tested yet

pubspec.lock

@@ -121,6 +121,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.19.1"
+  cross_file:
+    dependency: transitive
+    description:
+      name: cross_file
+      sha256: "7caf6a750a0c04effbb52a676dce9a4a592e10ad35c34d6d2d0e4811160d5670"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.3.4+2"
   crypto:
     dependency: transitive
     description:
@@ -201,6 +209,38 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "7.0.1"
+  file_selector_linux:
+    dependency: transitive
+    description:
+      name: file_selector_linux
+      sha256: "54cbbd957e1156d29548c7d9b9ec0c0ebb6de0a90452198683a7d23aed617a33"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.3+2"
+  file_selector_macos:
+    dependency: transitive
+    description:
+      name: file_selector_macos
+      sha256: "88707a3bec4b988aaed3b4df5d7441ee4e987f20b286cddca5d6a8270cab23f2"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.4+5"
+  file_selector_platform_interface:
+    dependency: transitive
+    description:
+      name: file_selector_platform_interface
+      sha256: a3994c26f10378a039faa11de174d7b78eb8f79e4dd0af2a451410c1a5c3f66b
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.6.2"
+  file_selector_windows:
+    dependency: transitive
+    description:
+      name: file_selector_windows
+      sha256: "320fcfb6f33caa90f0b58380489fc5ac05d99ee94b61aa96ec2bff0ba81d3c2b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.9.3+4"
   firebase_auth:
     dependency: "direct main"
     description:
@@ -249,6 +289,30 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.2.0"
+  firebase_storage:
+    dependency: "direct main"
+    description:
+      name: firebase_storage
+      sha256: d740b9ea0105f27d7286d7ad5957d778bf7fa967796c6e3fc26491cf5245b486
+      url: "https://pub.dev"
+    source: hosted
+    version: "13.0.3"
+  firebase_storage_platform_interface:
+    dependency: transitive
+    description:
+      name: firebase_storage_platform_interface
+      sha256: "52a1dfb2c93f49a8e800d4b9aed107d1c0f2f6dd3ebf10a5f7e2222442960e50"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.2.14"
+  firebase_storage_web:
+    dependency: transitive
+    description:
+      name: firebase_storage_web
+      sha256: d5ce115e3d5a58fddd7631d5246aa8389d8000fa7790ecb04f65bf751bbf6a92
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.10.21"
   fixnum:
     dependency: transitive
     description:
@@ -520,6 +584,78 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.5.4"
+  image_picker:
+    dependency: "direct main"
+    description:
+      name: image_picker
+      sha256: "736eb56a911cf24d1859315ad09ddec0b66104bc41a7f8c5b96b4e2620cf5041"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.0"
+  image_picker_android:
+    dependency: transitive
+    description:
+      name: image_picker_android
+      sha256: "58a85e6f09fe9c4484d53d18a0bd6271b72c53fce1d05e6f745ae36d8c18efca"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.8.13+5"
+  image_picker_for_web:
+    dependency: transitive
+    description:
+      name: image_picker_for_web
+      sha256: "40c2a6a0da15556dc0f8e38a3246064a971a9f512386c3339b89f76db87269b6"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.0"
+  image_picker_ios:
+    dependency: transitive
+    description:
+      name: image_picker_ios
+      sha256: e675c22790bcc24e9abd455deead2b7a88de4b79f7327a281812f14de1a56f58
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.8.13+1"
+  image_picker_linux:
+    dependency: transitive
+    description:
+      name: image_picker_linux
+      sha256: "1f81c5f2046b9ab724f85523e4af65be1d47b038160a8c8deed909762c308ed4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2"
+  image_picker_macos:
+    dependency: transitive
+    description:
+      name: image_picker_macos
+      sha256: "86f0f15a309de7e1a552c12df9ce5b59fe927e71385329355aec4776c6a8ec91"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2+1"
+  image_picker_platform_interface:
+    dependency: transitive
+    description:
+      name: image_picker_platform_interface
+      sha256: "9f143b0dba3e459553209e20cc425c9801af48e6dfa4f01a0fcf927be3f41665"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.11.0"
+  image_picker_windows:
+    dependency: transitive
+    description:
+      name: image_picker_windows
+      sha256: d248c86554a72b5495a31c56f060cf73a41c7ff541689327b1a7dbccc33adfae
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.2.2"
+  intl:
+    dependency: "direct main"
+    description:
+      name: intl
+      sha256: "3df61194eb431efc39c4ceba583b95633a403f46c9fd341e550ce0bfa50e9aa5"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.20.2"
   json_annotation:
     dependency: transitive
     description: