fix(android): drop geolocator for a native LocationManager channel

Removes the geolocator dependency, which transitively embedded
com.google.android.gms.* (play-services-location) — proprietary classes
that F-Droid's scanner rejects. The optional coarse-location button now
talks to Android's own LocationManager over a small platform channel
(org.comunes.tane/coarse_location): permission prompt, single coarse fix
with a 12s timeout, last-known fallback, null on any failure. Behavior
is unchanged and the CoarseLocationProvider interface is preserved, so
the UI, i18n and widget tests need no changes.

Also sets dependenciesInfo.includeInApk/Bundle = false so the AGP
dependency-metadata block (also flagged by F-Droid) is not embedded.
Neither change affects the Google Play build.

apps/app_seeds/test/services/coarse_location_test.dart

@@ -0,0 +1,59 @@
+import 'package:tane/services/coarse_location.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  const channel = MethodChannel('org.comunes.tane/coarse_location');
+  final messenger =
+      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger;
+
+  tearDown(() {
+    messenger.setMockMethodCallHandler(channel, null);
+    debugDefaultTargetPlatformOverride = null;
+  });
+
+  test('returns the lat/lon the platform channel provides', () async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.android;
+    messenger.setMockMethodCallHandler(channel, (call) async {
+      expect(call.method, 'getCoarseLatLon');
+      return {'lat': 41.39, 'lon': 2.16};
+    });
+
+    final loc = await const NativeCoarseLocation().currentCoarseLatLon();
+
+    expect(loc, isNotNull);
+    expect(loc!.lat, 41.39);
+    expect(loc.lon, 2.16);
+  });
+
+  test('returns null when the platform reports no fix (denied/off)', () async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.android;
+    messenger.setMockMethodCallHandler(channel, (call) async => null);
+
+    expect(await const NativeCoarseLocation().currentCoarseLatLon(), isNull);
+  });
+
+  test('returns null instead of throwing on a channel error', () async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.android;
+    messenger.setMockMethodCallHandler(channel, (call) async {
+      throw PlatformException(code: 'boom');
+    });
+
+    expect(await const NativeCoarseLocation().currentCoarseLatLon(), isNull);
+  });
+
+  test('returns null off Android without touching the channel', () async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.linux;
+    var invoked = false;
+    messenger.setMockMethodCallHandler(channel, (call) async {
+      invoked = true;
+      return {'lat': 1.0, 'lon': 1.0};
+    });
+
+    expect(await const NativeCoarseLocation().currentCoarseLatLon(), isNull);
+    expect(invoked, isFalse);
+  });
+}