feat: load Google Maps key dynamically from backend

- MapsService: obtiene la key via API e inyecta el script Maps JS en runtime
- LocationPickerDialog: muestra error descriptivo si la key no esta configurada
- index.html: eliminado script estatico de Maps

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/widgets/location_picker.dart

@@ -3,8 +3,8 @@ import 'package:flutter/material.dart';
 import 'package:geolocator/geolocator.dart';
 import 'package:google_maps_flutter/google_maps_flutter.dart';
 import 'package:http/http.dart' as http;
-
-const _mapsApiKey = String.fromEnvironment('MAPS_API_KEY', defaultValue: '');
+import 'package:prosapp_web_app/services/api_service.dart';
+import 'package:prosapp_web_app/services/maps_service.dart';
 
 class LocationResult {
   final LatLng position;
@@ -38,10 +38,23 @@ class _LocationPickerDialogState extends State<LocationPickerDialog> {
   String _city = '';
   bool _loading = true;
   bool _geocoding = false;
+  bool _mapsReady = false;
+  String? _mapsError;
 
   @override
   void initState() {
     super.initState();
+    _initMaps();
+  }
+
+  Future<void> _initMaps() async {
+    final ok = await MapsService.load();
+    if (!mounted) return;
+    if (!ok) {
+      setState(() { _loading = false; _mapsError = 'Google Maps no configurado. Configura la API Key en el panel de administración.'; });
+      return;
+    }
+    setState(() => _mapsReady = true);
     if (widget.initialPosition != null) {
       _position = widget.initialPosition!;
       _loading = false;
@@ -95,13 +108,15 @@ class _LocationPickerDialogState extends State<LocationPickerDialog> {
   }
 
   Future<void> _reverseGeocode(LatLng pos) async {
-    if (_mapsApiKey.isEmpty) return;
+    final keyData = await ApiService.instance.get('/settings/maps-key').catchError((_) => <String, dynamic>{});
+    final apiKey = keyData['api_key'] as String? ?? '';
+    if (apiKey.isEmpty) return;
     setState(() => _geocoding = true);
     try {
       final url = Uri.parse(
         'https://maps.googleapis.com/maps/api/geocode/json'
         '?latlng=${pos.latitude},${pos.longitude}'
-        '&key=$_mapsApiKey'
+        '&key=$apiKey'
         '&language=es',
       );
       final res = await http.get(url);
@@ -169,7 +184,16 @@ class _LocationPickerDialogState extends State<LocationPickerDialog> {
 
             // Map
             Expanded(
-              child: _loading
+              child: _mapsError != null
+                  ? Center(child: Padding(
+                      padding: const EdgeInsets.all(24),
+                      child: Column(mainAxisSize: MainAxisSize.min, children: [
+                        const Icon(Icons.map_outlined, size: 48, color: Colors.grey),
+                        const SizedBox(height: 12),
+                        Text(_mapsError!, textAlign: TextAlign.center, style: const TextStyle(color: Colors.grey)),
+                      ]),
+                    ))
+                  : _loading
                   ? const Center(child: CircularProgressIndicator())
                   : Stack(
                       children: [