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

bmi_calculator/pubspec.yaml

@@ -1,5 +1,5 @@
 name: bmi_calculator
-description: A new Flutter module project.
+description: A new Flutter project.
 
 version: 1.0.0+1
 
@@ -19,8 +19,3 @@ dev_dependencies:
 
 flutter:
   uses-material-design: true
-
-  module:
-    androidX: true
-    androidPackage: github.nisrulz.bmi_calculator
-    iosBundleIdentifier: github.nisrulz.bmiCalculator