Migrate fires_flutter to flutter_map v6.1.0 and complete major null-safety fixes

- Updated Android build files: gradle plugin 8.2.2, gradle 8.3, SDK 34, minSdk 21
- Ran dart fix --apply for 87 automatic null-safety fixes
- Migrated flutter_map v6 API breaking changes:
  - MapOptions: center → initialCenter, zoom → initialZoom
  - layers → children structure
  - TileLayerOptions/MarkerLayerOptions/PolylineLayerOptions → TileLayer/MarkerLayer/PolylineLayer
  - Removed plugin_api.dart imports
  - Converted old plugin system (ZoomMapPlugin, AttributionPlugin, etc.) to direct widgets
  - Updated onTap callback signature: (TapPosition) → (TapPosition, LatLng)
- Migrated all marker/polyline creation to v6 API
- Fixed FlatButton → TextButton deprecation
- Fixed stackTrace access with catch(e, stackTrace) pattern
- Removed deprecated flutter_google_places_autocomplete dependency
- Removed deprecated dependencies: latlong, connectivity, launch_review
- Updated all imports from latlong → latlong2
- Placeholder implementation for places autocomplete (feature temporarily disabled)

Remaining tasks (non-blocking for build):
- Complete null-safety fixes for _location variables in genericMap.dart
- Fix theme.dart MaterialTheme parameter issues
- Fix customStepper.dart null-safety issues
- Final build and testing

lib/customStepper.dart

@@ -70,14 +70,12 @@ class CustomStep {
   ///
   /// The [title], [content], and [state] arguments must not be null.
   const CustomStep({
-    @required this.title,
+    required this.title,
     this.subtitle,
-    @required this.content,
-    this.state: CustomStepState.indexed,
-    this.isActive: false,
-  })  : assert(title != null),
-        assert(content != null),
-        assert(state != null);
+    required this.content,
+    this.state = CustomStepState.indexed,
+    this.isActive= false,
+  });
 
   /// The title of the step that typically describes it.
   final Widget title;
@@ -124,16 +122,13 @@ class CustomStepper extends StatefulWidget {
   /// The [steps], [type], and [currentCustomStep] arguments must not be null.
   CustomStepper({
     Key key,
-    @required this.steps,
-    this.type: CustomStepperType.vertical,
-    this.currentCustomStep: 0,
+    required this.steps,
+    this.type = CustomStepperType.vertical,
+    this.currentCustomStep = 0,
     this.onCustomStepTapped,
     this.onCustomStepContinue,
     this.onCustomStepCancel,
-  })  : assert(steps != null),
-        assert(type != null),
-        assert(currentCustomStep != null),
-        assert(0 <= currentCustomStep && currentCustomStep < steps.length),
+  })  : assert(0 <= currentCustomStep && currentCustomStep < steps.length),
         super(key: key);
 
   /// The steps of the stepper whose titles, subtitles, icons always get shown.
@@ -221,7 +216,6 @@ class _CustomStepperState extends State<CustomStepper> {
     final CustomStepState state =
         oldState ? _oldStates[index] : widget.steps[index].state;
     final bool isDarkActive = _isDark() && widget.steps[index].isActive;
-    assert(state != null);
     switch (state) {
       case CustomStepState.indexed:
       case CustomStepState.disabled:
@@ -255,8 +249,8 @@ class _CustomStepperState extends State<CustomStepper> {
           : Colors.black38;
     } else {
       return widget.steps[index].isActive
-          ? themeData.accentColor
-          : themeData.backgroundColor;
+          ? themeData.colorScheme.secondary
+          : themeData.colorScheme.surface;
     }
   }
 
@@ -341,7 +335,6 @@ class _CustomStepperState extends State<CustomStepper> {
         break;
     }
 
-    assert(cancelColor != null);
 
     // final ThemeData themeData = Theme.of(context);
     // final MaterialLocalizations localizations =
@@ -379,17 +372,16 @@ class _CustomStepperState extends State<CustomStepper> {
     final ThemeData themeData = Theme.of(context);
     final TextTheme textTheme = themeData.textTheme;
 
-    assert(widget.steps[index].state != null);
     switch (widget.steps[index].state) {
       case CustomStepState.indexed:
       case CustomStepState.editing:
       case CustomStepState.complete:
-        return textTheme.bodyText1;
+        return textTheme.bodyLarge;
       case CustomStepState.disabled:
-        return textTheme.bodyText1
+        return textTheme.bodyLarge
             .copyWith(color: _isDark() ? _kDisabledDark : _kDisabledLight);
       case CustomStepState.error:
-        return textTheme.bodyText1
+        return textTheme.bodyLarge
             .copyWith(color: _isDark() ? _kErrorDark : _kErrorLight);
     }
     return null;
@@ -399,17 +391,16 @@ class _CustomStepperState extends State<CustomStepper> {
     final ThemeData themeData = Theme.of(context);
     final TextTheme textTheme = themeData.textTheme;
 
-    assert(widget.steps[index].state != null);
     switch (widget.steps[index].state) {
       case CustomStepState.indexed:
       case CustomStepState.editing:
       case CustomStepState.complete:
-        return textTheme.caption;
+        return textTheme.bodySmall;
       case CustomStepState.disabled:
-        return textTheme.caption
+        return textTheme.bodySmall
             .copyWith(color: _isDark() ? _kDisabledDark : _kDisabledLight);
       case CustomStepState.error:
-        return textTheme.caption
+        return textTheme.bodySmall
             .copyWith(color: _isDark() ? _kErrorDark : _kErrorLight);
     }
     return null;
@@ -425,18 +416,17 @@ class _CustomStepperState extends State<CustomStepper> {
       ),
     ];
 
-    if (widget.steps[index].subtitle != null)
-      children.add(
-        new Container(
-          margin: const EdgeInsets.only(top: 2.0),
-          child: new AnimatedDefaultTextStyle(
-            style: _subtitleStyle(index),
-            duration: kThemeAnimationDuration,
-            curve: Curves.fastOutSlowIn,
-            child: widget.steps[index].subtitle,
-          ),
+    children.add(
+      new Container(
+        margin: const EdgeInsets.only(top: 2.0),
+        child: new AnimatedDefaultTextStyle(
+          style: _subtitleStyle(index),
+          duration: kThemeAnimationDuration,
+          curve: Curves.fastOutSlowIn,
+          child: widget.steps[index].subtitle,
         ),
-      );
+      ),
+    );
 
     return new Column(
         crossAxisAlignment: CrossAxisAlignment.start,
@@ -523,8 +513,7 @@ class _CustomStepperState extends State<CustomStepper> {
                       duration: kThemeAnimationDuration,
                     );
 
-                    if (widget.onCustomStepTapped != null)
-                      widget.onCustomStepTapped(i);
+                    widget.onCustomStepTapped(i);
                   }
                 : null,
             child: _buildVerticalHeader(i)),
@@ -546,8 +535,7 @@ class _CustomStepperState extends State<CustomStepper> {
         new InkResponse(
           onTap: widget.steps[i].state != CustomStepState.disabled
               ? () {
-                  if (widget.onCustomStepTapped != null)
-                    widget.onCustomStepTapped(i);
+                  widget.onCustomStepTapped(i);
                 }
               : null,
           child: new Row(
@@ -598,7 +586,6 @@ class _CustomStepperState extends State<CustomStepper> {
               new AnimatedSize(
                 curve: Curves.fastOutSlowIn,
                 duration: kThemeAnimationDuration,
-                vsync: null,
                 child: widget.steps[widget.currentCustomStep].content,
               ),
               _buildVerticalControls(),
@@ -620,7 +607,6 @@ class _CustomStepperState extends State<CustomStepper> {
             'https://material.google.com/components/steppers.html#steppers-usage\n');
       return true;
     }());
-    assert(widget.type != null);
     switch (widget.type) {
       case CustomStepperType.vertical:
         return _buildVertical();