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/admin/update_settings.rs

@@ -3,11 +3,11 @@ use domain::DomainResult;
 use super::commands::UpdateSettingsCommand;
 use super::deps::AdminDeps;
 
-pub async fn execute(deps: &AdminDeps, cmd: UpdateSettingsCommand) -> DomainResult<()> {
+pub async fn execute(deps: &AdminDeps, cmd: UpdateSettingsCommand) -> DomainResult<Vec<(String, String)>> {
     for (key, value) in &cmd.settings {
         deps.settings_repo.set(key, value).await?;
     }
-    Ok(())
+    deps.settings_repo.get_all().await
 }
 
 #[cfg(test)]