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/rounded_btn.dart

@@ -0,0 +1,70 @@
+import 'package:flutter/material.dart';
+
+/// Rounded button widget with icon and text.
+/// Used primarily in the active fires page.
+class RoundedBtn extends StatelessWidget {
+  static const btnRadius = Radius.circular(90.0);
+
+  final IconData icon;
+  final String text;
+  final Color backColor;
+  final Color fontColor;
+  final TextStyle textStyle;
+  final VoidCallback onPressed;
+
+  const RoundedBtn({
+    required this.icon,
+    required this.text,
+    required this.onPressed,
+    required this.backColor,
+    this.textStyle = const TextStyle(fontSize: 20.0, color: Colors.white),
+    this.fontColor = Colors.white,
+  });
+
+  factory RoundedBtn.nav({
+    required IconData icon,
+    required String text,
+    required BuildContext context,
+    required String route,
+    required Color backColor,
+    TextStyle textStyle = const TextStyle(fontSize: 20.0, color: Colors.white),
+    Color fontColor = Colors.white,
+  }) {
+    return RoundedBtn(
+      icon: icon,
+      text: text,
+      onPressed: () {
+        Navigator.pushNamed(context, route);
+      },
+      backColor: backColor,
+      textStyle: textStyle,
+      fontColor: fontColor,
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return SizedBox(
+      child: ElevatedButton(
+        onPressed: onPressed,
+        style: ElevatedButton.styleFrom(
+          backgroundColor: backColor,
+          shape: RoundedRectangleBorder(
+            borderRadius: BorderRadius.all(btnRadius),
+          ),
+        ),
+        child: Padding(
+          padding: const EdgeInsets.all(10.0),
+          child: Row(
+            mainAxisSize: MainAxisSize.min,
+            children: <Widget>[
+              Icon(icon, size: 32.0, color: fontColor),
+              const SizedBox(width: 10.0),
+              Text(text, style: textStyle),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}