refactor: replace get_stream_url with get_source_uri per ADR-0002

Providers now expose a source URI (for FFmpeg) instead of a
viewer-facing stream URL. Playout Service will own transcoding.

- Add SourceUri value object (NetworkUrl | FilePath)
- Remove StreamQuality, StreamingProtocol from domain
- Simplify ProviderCapabilities (drop streaming_protocol, transcode)
- Jellyfin: return static direct stream URL
- Local files: return absolute file path
- Rename use case get_stream_url -> get_source
- Stream endpoint returns JSON SourceUri instead of 307 redirect

crates/application/src/library/tests/helpers.rs

@@ -4,10 +4,8 @@ use async_trait::async_trait;
 
 use domain::errors::DomainResult;
 use domain::models::MediaItem;
-use domain::ports::{
-    Collection, IProviderRegistry, ProviderCapabilities, SeriesSummary, StreamQuality,
-    StreamingProtocol,
-};
+use domain::ports::{Collection, IProviderRegistry, ProviderCapabilities, SeriesSummary};
+use domain::SourceUri;
 use domain::testing::{InMemoryLibraryRepository, NoopEventPublisher, NoopLibrarySync};
 use domain::value_objects::{ContentType, MediaFilter, MediaItemId};
 
@@ -29,11 +27,7 @@ impl IProviderRegistry for TestProviderRegistry {
         Ok(None)
     }
 
-    async fn get_stream_url(
-        &self,
-        _item_id: &MediaItemId,
-        _quality: &StreamQuality,
-    ) -> DomainResult<String> {
+    async fn get_source_uri(&self, _item_id: &MediaItemId) -> DomainResult<SourceUri> {
         Err(domain::DomainError::InfrastructureError(
             "TestProviderRegistry does not support streaming".into(),
         ))
@@ -55,9 +49,7 @@ impl IProviderRegistry for TestProviderRegistry {
             tags: false,
             decade: false,
             search: true,
-            streaming_protocol: StreamingProtocol::Hls,
             rescan: false,
-            transcode: false,
         })
     }