fix: allow deleting desktop providers

desktop/src-tauri/src/commands/providers.rs

@@ -77,9 +77,13 @@ pub async fn update_provider(
 
 #[tauri::command]
 pub async fn delete_provider(state: State<'_, AppState>, id: String) -> Result<(), String> {
-    // Virtual built-in providers have no DB row — deletion is a no-op (they'll reappear)
-    if id.starts_with("builtin_") {
-        return Ok(());
+    if let Some(builtin_id) = id.strip_prefix("builtin_") {
+        return boosapi_core::repo::provider::mark_builtin_provider_deleted(
+            &state.sea_db,
+            builtin_id,
+        )
+        .await
+        .map_err(|e| e.to_string());
     }
     boosapi_core::repo::provider::delete_provider(&state.sea_db, &id)
         .await