style(migrations): modernize type annotations

Update type annotations in initial schema migration:
- Use collections.abc.Sequence instead of typing.Sequence
- Use str | None union syntax instead of Union[str, None]
- Reorder imports alphabetically

Auto-fixed by ruff linter for Python 3.10+ compatibility.

Author: Sakeeb91

db/migrations/versions/20241124_0001_001_initial_schema.py

@@ -8,17 +8,16 @@
 including a query_history table for tracking SQL generation requests.
 """
 
-from typing import Sequence, Union
+from collections.abc import Sequence
 
-from alembic import op
 import sqlalchemy as sa
-
+from alembic import op
 
 # Revision identifiers, used by Alembic
 revision: str = "001"
-down_revision: Union[str, None] = None
-branch_labels: Union[str, Sequence[str], None] = None
-depends_on: Union[str, Sequence[str], None] = None
+down_revision: str | None = None
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
 
 
 def upgrade() -> None: