refactor: modernize code quality tooling with Ruff

- Replace black, isort, and flake8 with Ruff (all-in-one linter and formatter)
- Add comprehensive pyproject.toml configuration
- Simplify Makefile code quality targets
- Configure exclusions for venv/.venv in pyproject.toml
- Auto-fix 1,359 linting issues across codebase

Benefits:
- Much faster builds (Ruff is written in Rust)
- Single tool replaces multiple tools
- More comprehensive rule set (UP, B, C4, SIM, PIE, RET, Q)
- All configuration centralized in pyproject.toml
- Better import sorting and formatting consistency

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/utils/csv_processor.py

@@ -8,9 +8,9 @@ This module provides classes and functions for:
 """
 
 import logging
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from io import StringIO
-from typing import Any, Dict
+from typing import Any
 
 import pandas as pd
 import requests
@@ -145,7 +145,7 @@ class CSVProcessor:
         logger.info(f"Normalized columns: {list(df.columns)}")
         return df
 
-    def _clean_row_data(self, row_data: Dict[str, Any]) -> Dict[str, Any]:
+    def _clean_row_data(self, row_data: dict[str, Any]) -> dict[str, Any]:
         """Process a single row with data normalization."""
         # Handle NaN values
         processed_data = {k: (v if pd.notna(v) else None) for k, v in row_data.items()}
@@ -188,7 +188,7 @@ class CSVProcessor:
 
     async def process_marketplace_csv_from_url(
         self, url: str, marketplace: str, vendor_name: str, batch_size: int, db: Session
-    ) -> Dict[str, Any]:
+    ) -> dict[str, Any]:
         """
         Process CSV from URL with marketplace and vendor information.
 
@@ -245,7 +245,7 @@ class CSVProcessor:
         vendor_name: str,
         db: Session,
         batch_num: int,
-    ) -> Dict[str, int]:
+    ) -> dict[str, int]:
         """Process a batch of CSV rows with marketplace information."""
         imported = 0
         updated = 0
@@ -295,7 +295,7 @@ class CSVProcessor:
                             existing_product, key
                         ):
                             setattr(existing_product, key, value)
-                    existing_product.updated_at = datetime.now(timezone.utc)
+                    existing_product.updated_at = datetime.now(UTC)
                     updated += 1
                     logger.debug(
                         f"Updated product {product_data['marketplace_product_id']} for "