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/sqlite/src/wire.rs

@@ -1,6 +1,3 @@
-//! Wiring function that instantiates all SQLite repositories and returns them
-//! as trait-object Arcs.
-
 use std::sync::Arc;
 
 use sqlx::SqlitePool;
@@ -27,7 +24,6 @@ use crate::{
     user::SqliteUserRepository,
 };
 
-/// All SQLite adapter outputs, ready to be injected into the application layer.
 pub struct SqliteWireOutput {
     pub user_command: Arc<dyn UserCommand>,
     pub user_query: Arc<dyn UserQuery>,
@@ -45,10 +41,6 @@ pub struct SqliteWireOutput {
     pub transcode_settings: Arc<dyn TranscodeSettingsRepository>,
 }
 
-/// Create all SQLite repository implementations from a single pool.
-///
-/// Each struct wraps a clone of the same pool. Repositories that implement
-/// both Command and Query traits share a single `Arc` via `.clone()`.
 pub fn wire(pool: SqlitePool) -> SqliteWireOutput {
     let user = Arc::new(SqliteUserRepository::new(pool.clone()));
     let channel = Arc::new(SqliteChannelRepository::new(pool.clone()));