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

handling_routes/android/app/src/main/AndroidManifest.xml

@@ -14,6 +14,7 @@
          FlutterApplication and put your custom class here. -->
     <application android:name="${applicationName}" android:label="handling_routes" android:icon="@mipmap/ic_launcher">
         <activity android:name="io.flutter.embedding.android.FlutterActivity"
+                  android:exported="true"
                   android:launchMode="singleTop"
                   android:theme="@android:style/Theme.Black.NoTitleBar"
                   android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"

handling_routes/android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java

@@ -1,19 +0,0 @@
-package io.flutter.plugins;
-
-import androidx.annotation.Keep;
-import androidx.annotation.NonNull;
-import io.flutter.Log;
-
-import io.flutter.embedding.engine.FlutterEngine;
-
-/**
- * Generated file. Do not edit.
- * This file is generated by the Flutter tool based on the
- * plugins that support the Android platform.
- */
-@Keep
-public final class GeneratedPluginRegistrant {
-  private static final String TAG = "GeneratedPluginRegistrant";
-  public static void registerWith(@NonNull FlutterEngine flutterEngine) {
-  }
-}