Delete a bot file's chunks with the file

ON DELETE CASCADE only fires when PRAGMA foreign_keys is on, and only
src/server.ts turns it on. A script or CLI process deleting a bot file
therefore left every bot_file_chunks row behind, and the next
`bun run db:schema` failed with

    Foreign key violations after schema sync: bot_file_chunks -> bot_files

deleteBotFile and purgeStorage now delete the chunks themselves, so the
cascade is no longer load-bearing and a maintenance script behaves like
the server.

src/functions/backend/db/bot-files/delete-bot-file.ts

@@ -33,6 +33,13 @@ export default async function deleteBotFile({ scopes, file_id }: Params) {
     }
 
     await BunSQLite.sql({ sql: `DELETE FROM bot_file_vectors WHERE file_id = ?`, values: [file.id] });
+    /**
+     * Deleted here rather than left to the schema's cascade: SQLite has
+     * foreign keys off per connection unless `enableForeignKeys` ran, and
+     * a script or CLI process that deletes a file would otherwise leave
+     * its chunks behind, which then fail the next schema sync.
+     */
+    await BunSQLite.sql({ sql: `DELETE FROM bot_file_chunks WHERE file_id = ?`, values: [file.id] });
     await BunSQLite.sql({ sql: `DELETE FROM bot_files WHERE id = ?`, values: [file.id] });
     /**
      * Its pending ingestion would only find nothing left.