feat: enhance backup process with lease management and attachment deletion

- Implemented a backup runner lease mechanism to prevent concurrent backup executions.
- Added `deleteAllAttachmentsForCiphers` function to delete attachments for multiple ciphers efficiently.
- Introduced `bulkDeleteAttachmentsByIds` method in storage to handle batch deletion of attachments.
- Updated backup execution logic to utilize the new lease management and ensure timely updates during the backup process.
- Refactored cipher deletion to handle attachments more effectively.
- Improved website icon loading with a dedicated caching mechanism for better performance.
- Added new index on `ciphers` table for `folder_id` to optimize queries related to folder management.
- Enhanced response handling for CORS policy to allow credentials for specific origins.

src/services/storage-schema.ts

@@ -29,6 +29,7 @@ const SCHEMA_STATEMENTS: readonly string[] = [
   'CREATE INDEX IF NOT EXISTS idx_ciphers_user_archived ON ciphers(user_id, archived_at)',
   'CREATE INDEX IF NOT EXISTS idx_ciphers_user_deleted ON ciphers(user_id, deleted_at)',
   'CREATE INDEX IF NOT EXISTS idx_ciphers_user_deleted_updated ON ciphers(user_id, deleted_at, updated_at)',
+  'CREATE INDEX IF NOT EXISTS idx_ciphers_user_folder ON ciphers(user_id, folder_id)',
 
   'CREATE TABLE IF NOT EXISTS folders (' +
   'id TEXT PRIMARY KEY, user_id TEXT NOT NULL, name TEXT NOT NULL, created_at TEXT NOT NULL, updated_at TEXT NOT NULL, ' +