refactor: clean up 55 lint warnings and issues

- Remove all 31 avoid_print debug statements across codebase
- Fix 8 critical warnings (unused variables, unreachable defaults, etc)
- Update deprecated APIs: launch() → launchUrl(), textScaleFactor → textScaler
- Replace deprecated surfaceVariant → surfaceContainerHighest in Material 3 themes
- Refactor switch statements to use modern pattern matching
- Remove unused code: _showDialog, _initNoLocation, _getAnchorOffset
- Fix use_build_context_synchronously by adding mounted checks
- Add ignore_for_file annotations to generated JSON serialization files
- Fix type annotations in appState.dart and models

Warnings reduced from 301 to 246 issues (8 → 0 critical warnings).
Build verified: app-production-debug.apk (160MB) compiles successfully.
Zero type errors, Dart analysis clean for critical issues.

lib/supportPage.dart

@@ -25,8 +25,11 @@ class _SupportPageState extends State<SupportPage> {
       child: OutlinedButton.icon(
         icon: const Icon(Icons.favorite_border),
         label: Text(S.of(context).comunesSupportBtn),
-        onPressed: () {
-          launch('https://comunes.org/');
+        onPressed: () async {
+          final Uri url = Uri.parse('https://comunes.org/');
+          if (await canLaunchUrl(url)) {
+            await launchUrl(url);
+          }
         },
       ),
     );
@@ -65,9 +68,12 @@ class _SupportPageState extends State<SupportPage> {
       child: OutlinedButton.icon(
         icon: const Icon(Icons.translate),
         label: Text(S.of(context).translateBtn),
-        onPressed: () {
-          launch(
+        onPressed: () async {
+          final Uri url = Uri.parse(
               'https://translate.comunes.org/projects/todos-contra-el-fuego/');
+          if (await canLaunchUrl(url)) {
+            await launchUrl(url);
+          }
         },
       ),
     );
@@ -77,8 +83,7 @@ class _SupportPageState extends State<SupportPage> {
   Widget build(BuildContext context) {
     return Scaffold(
         key: _scaffoldKey,
-        appBar:
-            AppBar(title: Text(S.of(context).supportThisInitiative)),
+        appBar: AppBar(title: Text(S.of(context).supportThisInitiative)),
         drawer: MainDrawer(context, SupportPage.routeName),
         body: Padding(
           padding: const EdgeInsets.all(8.0),