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/widgets/material_app_with_intro.dart

@@ -0,0 +1,84 @@
+import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'dart:async';
+
+abstract class MaterialAppWithIntro extends StatelessWidget {
+  final String name;
+  final ThemeData theme;
+  final Map<String, WidgetBuilder> routes;
+  final WidgetBuilder introWidget;
+  final WidgetBuilder continueWidget;
+  final String prefsKey;
+
+  MaterialAppWithIntro(this.name, this.theme, this.routes, this.introWidget,
+      this.continueWidget, this.prefsKey);
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: MaterialAppWithIntroHome(introWidget, continueWidget, prefsKey),
+      title: name,
+      theme: theme,
+      routes: routes,
+    );
+  }
+}
+
+class MaterialAppWithIntroHome extends StatefulWidget {
+  final WidgetBuilder introWidget;
+  final WidgetBuilder continueWidget;
+  final String prefsKey;
+
+  const MaterialAppWithIntroHome(
+      this.introWidget, this.continueWidget, this.prefsKey);
+
+  @override
+  _MaterialAppWithIntroState createState() =>
+      _MaterialAppWithIntroState(introWidget, continueWidget, prefsKey);
+}
+
+class _MaterialAppWithIntroState extends State<MaterialAppWithIntroHome> {
+  final WidgetBuilder introWidget;
+  final WidgetBuilder continueWidget;
+  final String prefsKey;
+
+  _MaterialAppWithIntroState(
+      this.introWidget, this.continueWidget, this.prefsKey);
+
+  @override
+  void initState() {
+    super.initState();
+    Timer(const Duration(milliseconds: 1000), () {
+      checkFirstStart();
+    });
+  }
+
+  // https://stackoverflow.com/questions/50654195/flutter-one-time-intro-screen
+  Future<void> checkFirstStart() async {
+    final String initialWizardKey = prefsKey;
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    final bool showInitialWizard = (prefs.getBool(initialWizardKey) ?? true);
+
+    if (showInitialWizard) {
+      await prefs.setBool(initialWizardKey, false);
+      if (mounted) {
+        await Navigator.of(context)
+            .pushReplacement(MaterialPageRoute(builder: introWidget));
+      }
+    } else {
+      if (mounted) {
+        await Navigator.of(context)
+            .pushReplacement(MaterialPageRoute(builder: continueWidget));
+      }
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Center(
+        child: CircularProgressIndicator(),
+      ),
+    );
+  }
+}