fix: resolve ruff lint errors in migration and registry telemetry

Remove unused imports (sqlalchemy, UUID) from migration 0011 and
remove stale noqa directive from registry_telemetry.py.

Signed-off-by: Shaan Narendran <shaannaren06@gmail.com>

Author: ShaanNarendran

observal-server/alembic/versions/0011_agent_review_and_bundles.py

@@ -12,8 +12,6 @@
 """
 
 from alembic import op
-import sqlalchemy as sa
-from sqlalchemy.dialects.postgresql import UUID
 
 revision = "0011"
 down_revision = "0010"

observal-server/services/registry_telemetry.py

@@ -16,7 +16,7 @@
 logger = logging.getLogger(__name__)
 
 # prevent GC of fire-and-forget tasks (same pattern as telemetry.py)
-_background_tasks: set[asyncio.Task] = set()  # noqa: RUF012
+_background_tasks: set[asyncio.Task] = set()
 
 
 async def _emit(trace: dict, span: dict, audit: dict):