fix(presentation): extract 12 handler violations to use cases

- TokenService port + JwtTokenService adapter; login/refresh return LoginResult
- delete get_token (dup of login); create_tokens helper removed
- type UpdateChannelRequest schedule_config/recycle_policy (no serde_json::Value)
- update_settings returns updated Vec; handler calls one use case
- config use case in application::config; handler maps DTO only
- SyncStatusEntry moved to api-types w/ From<LibrarySyncLogEntry>
- trigger_sync: Conflict error, drop sync_trigger.send from handler
- UpsertProviderCommand.config accepts Value; serialization in use case
- get_current_broadcast returns BroadcastWithChannel; one call
- get_stream_url resolves broadcast internally; handler single call

crates/application/src/library/sync.rs

@@ -14,7 +14,7 @@ pub async fn execute(
 
     for pid in &provider_ids {
         if deps.library_query.is_sync_running(pid).await? {
-            return Err(DomainError::ValidationError(format!(
+            return Err(DomainError::Conflict(format!(
                 "Sync already running for provider '{pid}'"
             )));
         }