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/data_processing.py

@@ -9,7 +9,6 @@ This module provides classes and functions for:
 
 import logging
 import re
-from typing import Optional, Tuple
 
 import pandas as pd
 
@@ -21,7 +20,7 @@ class GTINProcessor:
 
     VALID_LENGTHS = [8, 12, 13, 14]  # List of valid GTIN lengths
 
-    def normalize(self, gtin_value: any) -> Optional[str]:
+    def normalize(self, gtin_value: any) -> str | None:
         """
         Normalize GTIN to proper format.
 
@@ -55,11 +54,11 @@ class GTINProcessor:
             # Standard lengths - pad appropriately
             if length == 8:
                 return gtin_clean.zfill(8)  # EAN-8
-            elif length == 12:
+            if length == 12:
                 return gtin_clean.zfill(12)  # UPC-A
-            elif length == 13:
+            if length == 13:
                 return gtin_clean.zfill(13)  # EAN-13
-            elif length == 14:
+            if length == 14:
                 return gtin_clean.zfill(14)  # GTIN-14
 
         elif length > 14:
@@ -111,7 +110,7 @@ class PriceProcessor:
 
     def parse_price_currency(
         self, price_str: any
-    ) -> Tuple[Optional[str], Optional[str]]:
+    ) -> tuple[str | None, str | None]:
         """
         Parse a price string to extract the numeric value and currency.