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/genericMap.dart

@@ -1,6 +1,5 @@
 import 'dart:core';
 
-import 'package:comunes_flutter/comunes_flutter.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_map/flutter_map.dart';
 import 'package:flutter_redux/flutter_redux.dart';
@@ -334,7 +333,8 @@ class GenericMapState extends State<GenericMap> {
                           top: constraints.maxHeight - 200,
                           right: 10.0,
                           left: 10.0,
-                          child: CenteredRow(
+                          child: Row(
+                              mainAxisAlignment: MainAxisAlignment.center,
                               // Fit sample:
                               // https://github.com/apptreesoftware/flutter_map/blob/master/flutter_map_example/lib/pages/map_controller.dart
                               children: status ==
@@ -401,8 +401,11 @@ class GenericMapState extends State<GenericMap> {
     // const calibrate = false; // useful when we change the fire icons size
     for (final dynamic falsePos in falsePosList) {
       try {
-        final List<dynamic> coords =
-            falsePos['geo']['coordinates'] as List<dynamic>;
+        final Map<String, dynamic> falsePosMap =
+            falsePos as Map<String, dynamic>;
+        final Map<String, dynamic> geo =
+            falsePosMap['geo'] as Map<String, dynamic>;
+        final List<dynamic> coords = geo['coordinates'] as List<dynamic>;
         // print('false pos: ${coords}');
         final LatLng loc = LatLng(
             (coords[1] as num).toDouble(), (coords[0] as num).toDouble());