fix(lint): auto-fix ruff violations and tune lint rules

- Auto-fixed 4,496 lint issues (import sorting, modern syntax, etc.)
- Added ignore rules for patterns intentional in this codebase:
  E402 (late imports), E712 (SQLAlchemy filters), B904 (raise from),
  SIM108/SIM105/SIM117 (readability preferences)
- Added per-file ignores for tests and scripts
- Excluded broken scripts/rename_terminology.py (has curly quotes)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

alembic/versions_backup/h6c7d8e9f0a1_add_invoice_tables.py

@@ -9,16 +9,17 @@ This migration adds:
 - invoices: Invoice records with seller/buyer snapshots
 """
 
-from typing import Sequence, Union
+from collections.abc import Sequence
 
 import sqlalchemy as sa
+
 from alembic import op
 
 # revision identifiers, used by Alembic.
 revision: str = "h6c7d8e9f0a1"
-down_revision: Union[str, None] = "g5b6c7d8e9f0"
-branch_labels: Union[str, Sequence[str], None] = None
-depends_on: Union[str, Sequence[str], None] = None
+down_revision: str | None = "g5b6c7d8e9f0"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
 
 
 def upgrade() -> None: