cleanup: strip comments, extract constants, DRY shared helpers across adapters + infra-wiring

- strip all comments except WHY workaround notes (3 remain)
- remove all #[allow(dead_code)]; fix via _prefix rename
- extract named constants: JWT time units, token types, default config values, jellyfin fallback bitrate
- DRY: move serialize_enum_as_string, content_type_str, parse_content_type, parse_genres_blob to adapter-common
- sqlite+postgres library.rs use shared helpers instead of local copies
- sqlite+postgres channel.rs use shared serialize_enum_as_string
- remove dead `let _ = ext` in scanner.rs

crates/adapters/event-publisher/src/lib.rs

@@ -26,7 +26,7 @@ impl ChannelEventBus {
 #[async_trait]
 impl EventPublisher for ChannelEventBus {
     async fn publish(&self, event: DomainEvent) -> DomainResult<()> {
-        let _ = self.tx.send(event); // Ok to drop if no receivers
+        let _ = self.tx.send(event);
         Ok(())
     }
 }
@@ -34,9 +34,6 @@ impl EventPublisher for ChannelEventBus {
 #[async_trait]
 impl EventConsumer for ChannelEventBus {
     async fn recv(&self) -> DomainResult<DomainEvent> {
-        // Note: This creates a new subscriber each call — for real use,
-        // the presentation layer should hold a receiver from subscriber()
-        // This impl exists to satisfy the port trait
         let mut rx = self.tx.subscribe();
         rx.recv()
             .await