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/api-types/src/config.rs

@@ -1,8 +1,6 @@
 use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
 
-use crate::common::enum_to_string;
-
 #[derive(Debug, Clone, Serialize, Deserialize, ToSchema)]
 pub struct ProviderCapabilitiesResponse {
     pub collections: bool,
@@ -11,9 +9,7 @@ pub struct ProviderCapabilitiesResponse {
     pub tags: bool,
     pub decade: bool,
     pub search: bool,
-    pub streaming_protocol: String,
     pub rescan: bool,
-    pub transcode: bool,
 }
 
 impl From<domain::ports::ProviderCapabilities> for ProviderCapabilitiesResponse {
@@ -25,9 +21,7 @@ impl From<domain::ports::ProviderCapabilities> for ProviderCapabilitiesResponse
             tags: c.tags,
             decade: c.decade,
             search: c.search,
-            streaming_protocol: enum_to_string(&c.streaming_protocol),
             rescan: c.rescan,
-            transcode: c.transcode,
         }
     }
 }