refactor: standardize Dart and Android config across all 54 apps

- Bump all apps to sdk >=3.0.0 <4.0.0 and add flutter_lints + a shared
  analysis_options.yaml to every app (flutter analyze is now green repo-wide)
- Fix real compile errors in firebase_google_authentication and image_editor,
  plus deprecated APIs (Matrix4, SvgPicture.color, textScaleFactor),
  missing async 'mounted' guards, and misc lints via dart fix + manual fixes
- Align pubspec 'name' with each folder and Android namespace/applicationId
  with the documented github.nisrulz.* convention
- Convert bmi_calculator from a legacy Flutter module to a standard app
  with a proper android/ scaffold; fix missing android:exported in launcher
  manifests across 22 apps so all Android builds pass
- Untrack generated build files (GeneratedPluginRegistrant,
  .flutter-plugins-dependencies) and ignore them

.gitignore

@@ -351,6 +351,11 @@ build/
 
 **/flutter_export_environment.sh
 **/.dart_tool
+**/.flutter-plugins-dependencies
+**/GeneratedPluginRegistrant.java
+**/GeneratedPluginRegistrant.h
+**/GeneratedPluginRegistrant.m
+**/GeneratedPluginRegistrant.swift
 .pr-description-*/
 
 .trash/