Implement public ShareViewerScreen with Android deep-link intent-filter (9b)

- New ShareViewerScreen (/share/:token): unauthenticated share-viewer that
  fetches share metadata via publicApiClientProvider, renders filename, type,
  duration, thumbnail, and a Play button routing to the video/audio player.
- New publicApiClientProvider: bare Dio client (no auth interceptors) for the
  public share endpoint; shares kPlayerBaseUrl with the authenticated client.
- AndroidManifest: http + https deep-link intent-filters for /share/.* so
  Android routes share URLs directly into the app (App Links / autoVerify).
- router.dart: /share/:token bypasses the authentication redirect; guard uses
  AppRoutes.shareViewerPrefix constant instead of a raw '/share/' string (DIP).
- app_routes.dart: shareViewer route constant, shareViewerPrefix, shareViewerPath helper.
- error_mappers.dart: shareViewerErrorMessage — 404 invalid/revoked, 410 expired.
- player_api_client.dart: baseUrl getter encapsulates rawDio.options.baseUrl so
  screens never access transport internals directly (ISP, DIP).
- Review fixes: OCP icon map in _FallbackThumbnail, LSP explicit baseUrl
  overrides in test fakes, DIP shareViewerPrefix constant.

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

1 files changed, 12 insertions, 6 deletions

diff --git a/player-android/lib/providers/api_client_provider.dart b/player-android/lib/providers/api_client_provider.dart
index 128b89d..9a3ca8d 100644
--- a/player-android/lib/providers/api_client_provider.dart
+++ b/player-android/lib/providers/api_client_provider.dart
@@ -5,12 +5,18 @@ import '../api/dio_player_api_client.dart';
 import '../api/player_api_client.dart';
 import '../navigation_key.dart';
 
-/// Base URL for the player-server API.
+/// Base URL for the player-server API, resolved at compile time via
+/// the PLAYER_BASE_URL environment variable (or the default below).
 ///
-/// In production this is injected from the environment or a config file.
-/// The default points to a local dev instance so the app is runnable
-/// without extra configuration.
-const _kBaseUrl = String.fromEnvironment(
+/// Declared as a package-level identifier (no underscore) so it can be
+/// shared by [publicApiClientProvider] in [public_api_client_provider.dart].
+/// The value is set once at compile time and never changes at runtime,
+/// making it safe to share across providers.
+///
+/// In production this is injected via `--dart-define=PLAYER_BASE_URL=...`.
+/// The default points to the Android emulator host loopback address so the
+/// app is runnable out-of-the-box without extra configuration.
+const kPlayerBaseUrl = String.fromEnvironment(
   'PLAYER_BASE_URL',
   defaultValue: 'http://10.0.2.2:8080',
 );
@@ -34,7 +40,7 @@ final apiClientProvider = Provider<PlayerApiClient>((ref) {
   final storage = ref.watch(tokenStorageProvider);
 
   final dioClient = DioClient(
-    baseUrl: Uri.parse(_kBaseUrl),
+    baseUrl: Uri.parse(kPlayerBaseUrl),
     storage: storage,
     // Share the navigator key with go_router so 401 redirects go through the
     // correct router instance rather than the raw Navigator.