fix(lint): pin ruff version, add pre-commit hook, fix all lint errors

- Pin ruff==0.8.4 in requirements-dev.txt (was >=0.8.4, CI got newer
  version with different import sorting rules)
- Add ruff to .pre-commit-config.yaml with --fix to auto-sort imports
  on commit (prevents PyCharm import reordering from reaching CI)
- Fix I001 import sorting in 6 files
- Fix F401 unused import (sqlalchemy.Numeric in subscription.py)
- Fix noqa false positive in validate_architecture.py comment

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

.pre-commit-config.yaml

@@ -29,15 +29,9 @@ repos:
       - id: check-merge-conflict
       - id: debug-statements
 
-  # Python formatting (optional - uncomment if you want)
-  # - repo: https://github.com/psf/black
-  #   rev: 23.12.1
-  #   hooks:
-  #     - id: black
-  #       language_version: python3
-
-  # Python import sorting (optional)
-  # - repo: https://github.com/pycqa/isort
-  #   rev: 5.13.2
-  #   hooks:
-  #     - id: isort
+  # Ruff - linting and import sorting (replaces black + isort)
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.8.4
+    hooks:
+      - id: ruff
+        args: [--fix, --exit-non-zero-on-fix]

app/modules/analytics/services/stats_service.py

@@ -21,7 +21,10 @@ from sqlalchemy.orm import Session
 from app.modules.catalog.models import Product  # IMPORT-002
 from app.modules.customers.models.customer import Customer  # IMPORT-002
 from app.modules.inventory.models import Inventory  # IMPORT-002
-from app.modules.marketplace.models import MarketplaceImportJob, MarketplaceProduct  # IMPORT-002
+from app.modules.marketplace.models import (  # IMPORT-002
+    MarketplaceImportJob,
+    MarketplaceProduct,
+)
 from app.modules.orders.models import Order  # IMPORT-002
 from app.modules.tenancy.exceptions import (
     AdminOperationException,

app/modules/billing/models/subscription.py

@@ -22,7 +22,6 @@ from sqlalchemy import (
     ForeignKey,
     Index,
     Integer,
-    Numeric,
     String,
     Text,
 )

app/modules/billing/schemas/__init__.py

@@ -21,8 +21,6 @@ from app.modules.billing.schemas.billing import (
     CancelRequest,
     CancelResponse,
     CategoryListResponse,
-    ChangeTierRequest as BillingChangeTierRequest,
-    ChangeTierResponse as BillingChangeTierResponse,
     # Checkout & Portal schemas
     CheckoutRequest,
     CheckoutResponse,
@@ -56,12 +54,18 @@ from app.modules.billing.schemas.billing import (
     SubscriptionTierListResponse,
     SubscriptionTierResponse,
     SubscriptionTierUpdate,
-    TierListResponse,
-    TierResponse,
     # Subscription Tier Admin schemas
     TierFeatureLimitEntry,
+    TierListResponse,
+    TierResponse,
     UpcomingInvoiceResponse,
 )
+from app.modules.billing.schemas.billing import (
+    ChangeTierRequest as BillingChangeTierRequest,
+)
+from app.modules.billing.schemas.billing import (
+    ChangeTierResponse as BillingChangeTierResponse,
+)
 from app.modules.billing.schemas.subscription import (
     ChangeTierRequest,
     ChangeTierResponse,

app/modules/messaging/routes/api/storefront.py

@@ -32,7 +32,10 @@ from app.modules.messaging.exceptions import (
     ConversationClosedException,
     ConversationNotFoundException,
 )
-from app.modules.messaging.models.message import ConversationType, ParticipantType  # API-007
+from app.modules.messaging.models.message import (  # API-007
+    ConversationType,
+    ParticipantType,
+)
 from app.modules.messaging.schemas import (
     ConversationDetailResponse,
     ConversationListResponse,

app/modules/monitoring/models/__init__.py

@@ -5,10 +5,9 @@ Monitoring module database models.
 Provides monitoring-related models including capacity snapshots.
 """
 
-from app.modules.monitoring.models.capacity_snapshot import CapacitySnapshot
-
 # Admin notification and logging models
 from app.modules.messaging.models import AdminNotification
+from app.modules.monitoring.models.capacity_snapshot import CapacitySnapshot
 from app.modules.tenancy.models import PlatformAlert
 
 __all__ = [

app/modules/monitoring/services/__init__.py

@@ -9,14 +9,14 @@ from app.modules.monitoring.services.admin_audit_service import (
     AdminAuditService,
     admin_audit_service,
 )
-from app.modules.monitoring.services.capacity_forecast_service import (
-    CapacityForecastService,
-    capacity_forecast_service,
-)
 from app.modules.monitoring.services.background_tasks_service import (
     BackgroundTasksService,
     background_tasks_service,
 )
+from app.modules.monitoring.services.capacity_forecast_service import (
+    CapacityForecastService,
+    capacity_forecast_service,
+)
 from app.modules.monitoring.services.log_service import (
     LogService,
     log_service,

main.py

@@ -26,11 +26,11 @@ from fastapi import Depends, FastAPI, HTTPException, Request, Response
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse, HTMLResponse, RedirectResponse
 from fastapi.staticfiles import StaticFiles
-from uvicorn.middleware.proxy_headers import ProxyHeadersMiddleware
 from sentry_sdk.integrations.fastapi import FastApiIntegration
 from sentry_sdk.integrations.sqlalchemy import SqlalchemyIntegration
 from sqlalchemy import text
 from sqlalchemy.orm import Session
+from uvicorn.middleware.proxy_headers import ProxyHeadersMiddleware
 
 from app.api.main import api_router
 from app.core.config import settings

requirements-dev.txt

@@ -5,7 +5,7 @@ alembic>=1.14.0
 # Linting and formatting tools
 black>=24.10.0
 isort>=5.13.2
-ruff>=0.8.4  # Modern alternative to flake8, faster and Python 3.13 compatible
+ruff==0.8.4  # Pinned — must match pre-commit hook and local version
 mypy>=1.13.0
 
 # Optional: More advanced linting (if you prefer flake8 over ruff)

scripts/validate/validate_architecture.py

@@ -4663,7 +4663,7 @@ class ArchitectureValidator:
                     if imported_module == module_name:
                         continue
 
-                    # Skip suppression comments (# IMPORT-002 or # noqa: import-002)
+                    # Skip suppression comments (# IMPORT-002)
                     if "import-002" in line.lower():
                         continue
 

tests/integration/middleware/conftest.py

@@ -26,8 +26,8 @@ from main import app
 from tests.integration.middleware.middleware_test_routes import (
     admin_router,
     api_router,
-    storefront_router,
     store_router,
+    storefront_router,
 )
 from tests.integration.middleware.middleware_test_routes import (
     router as test_router,