Fix linting errors across backend and frontend

Backend: auto-fix and format all ruff issues, manually fix B904/B023/
SIM117/B007/E741/F841 errors, suppress B008 (FastAPI Depends) and F821
(SQLAlchemy forward refs) in config. Frontend: allow constant exports,
disable React compiler-specific rules (set-state-in-effect,
preserve-manual-memoization).

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

backend/src/app/alembic/versions/c3d4e5f6a7b8_add_route_grouping.py

@@ -5,26 +5,26 @@ Revises: b2c3d4e5f6a7
 Create Date: 2026-02-06 12:00:00.000000
 
 """
-from typing import Sequence, Union
 
-from alembic import op
+from collections.abc import Sequence
+
 import sqlalchemy as sa
-
+from alembic import op
 
 # revision identifiers, used by Alembic.
-revision: str = 'c3d4e5f6a7b8'
-down_revision: Union[str, Sequence[str], None] = 'b2c3d4e5f6a7'
-branch_labels: Union[str, Sequence[str], None] = None
-depends_on: Union[str, Sequence[str], None] = None
+revision: str = "c3d4e5f6a7b8"
+down_revision: str | Sequence[str] | None = "b2c3d4e5f6a7"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
 
 
 def upgrade() -> None:
     op.add_column(
-        'routes',
+        "routes",
         sa.Column(
-            'parent_route_id',
+            "parent_route_id",
             sa.Integer(),
-            sa.ForeignKey('routes.id', ondelete='CASCADE'),
+            sa.ForeignKey("routes.id", ondelete="CASCADE"),
             nullable=True,
             index=True,
         ),
@@ -32,4 +32,4 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
-    op.drop_column('routes', 'parent_route_id')
+    op.drop_column("routes", "parent_route_id")