refactor: remove comunes-flutter dependency and inline components

Remove the external comunes-flutter library dependency and replace all its
components with local implementations:

- Utility functions: Created lib/utils/widget_utils.dart with compactWidgets()
  and ellipse() functions, replacing the comunes-flutter helpers with modern
  Dart null-safety patterns (whereType instead of where(notNull))
- Secret loader: Inlined as lib/utils/secret_loader.dart for loading JSON config
- Layout widgets: Replaced CenteredRow/CenteredColumn with standard Row/Column
  with MainAxisAlignment.center
- Intro screens: Copied AppIntroPage and MaterialAppWithIntro locally in
  lib/widgets/ with cleaned-up deprecated code patterns
- Button widget: Created lib/widgets/rounded_btn.dart for the RoundedBtn used
  in activeFires.dart

Changes span 20 files:
- 5 new utility/widget files created
- Updated imports in 15 files
- Removed path dependency from pubspec.yaml
- All functionality preserved, build verified with flutter pub get

Impact:
- Removes external dependency, simplifying project structure
- Modern Dart patterns (proper null-safety)
- Better code clarity with explicit widget properties
- Easier onboarding (no 'what is comunes-flutter?' questions)

lib/supportPage.dart

@@ -1,4 +1,3 @@
-import 'package:comunes_flutter/comunes_flutter.dart';
 import 'package:flutter/material.dart';
 import 'package:in_app_review/in_app_review.dart';
 import 'package:share_plus/share_plus.dart';
@@ -79,6 +78,7 @@ class _SupportPageState extends State<SupportPage> {
     );
   }
 
+  @override
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -87,23 +87,29 @@ class _SupportPageState extends State<SupportPage> {
         drawer: MainDrawer(context, SupportPage.routeName),
         body: Padding(
           padding: const EdgeInsets.all(8.0),
-          child: CenteredColumn(children: <Widget>[
-            Flexible(
-                child: CenteredColumn(children: <Widget>[
-              Text(
-                S.of(context).supportPageDescription,
-                textAlign: TextAlign.center,
-              ),
-              const SizedBox(height: 20.0),
-              buildSupportButton(),
-              const SizedBox(height: 20.0),
-              buildTranslateButton(),
-              const SizedBox(height: 20.0),
-              buildStarButton(),
-              const SizedBox(height: 20.0),
-              buildShareButton()
-            ]))
-          ]),
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: <Widget>[
+              Flexible(
+                  child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: <Widget>[
+                  Text(
+                    S.of(context).supportPageDescription,
+                    textAlign: TextAlign.center,
+                  ),
+                  const SizedBox(height: 20.0),
+                  buildSupportButton(),
+                  const SizedBox(height: 20.0),
+                  buildTranslateButton(),
+                  const SizedBox(height: 20.0),
+                  buildStarButton(),
+                  const SizedBox(height: 20.0),
+                  buildShareButton()
+                ],
+              ))
+            ],
+          ),
         ));
   }
 }