Optimize android's Gradle settings and clean up mobile source code (#240)

* optimize android side gradle settings

* android minsdk back to 21

* remove unused package, update linter and fix lint error

mobile/pubspec.yaml

@@ -10,7 +10,7 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
-  cupertino_icons: ^1.0.2
+
   photo_manager: ^2.0.6
   flutter_hooks: ^0.18.0
   hooks_riverpod: ^2.0.0-dev.0
@@ -23,12 +23,10 @@ dependencies:
   auto_route: ^4.0.1
   exif: ^3.1.1
   transparent_image: ^2.0.0
-  visibility_detector: ^0.2.2
   flutter_launcher_icons: "^0.9.2"
   fluttertoast: ^8.0.8
   video_player: ^2.2.18
   chewie: ^1.2.2
-  sliver_tools: ^0.2.5
   badges: ^2.0.2
   photo_view: ^0.14.0
   socket_io_client: ^2.0.0-beta.4-nullsafety.0
@@ -43,10 +41,17 @@ dependencies:
   http: 0.13.4
   cancellation_token_http: ^1.1.0
 
+  path: ^1.8.1
+  path_provider: ^2.0.11
+  latlong2: ^0.8.1
+  collection: ^1.16.0
+  http_parser: ^4.0.1
+
+
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  flutter_lints: ^1.0.0
+  flutter_lints: ^2.0.1
   hive_generator: ^1.1.2
   build_runner: ^2.1.7
   auto_route_generator: ^4.0.0