refactor: Convert to UV Python project with proper package structure

- Restructured project to use src/stocktool package layout
- Migrated to UV for dependency management
- Added pyproject.toml with all dependencies (sv-ttk, pillow, requests, pyyaml)
- Organized test files into tests/ directory
- Updated .gitignore for UV projects
- Comprehensive README with installation and usage instructions
- Removed old unused files (main.py, stock_tool_gui.py, duplicate copy)
- Added CLI entry point: stock-tool command

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

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

tests/test_stock_level.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""Test script to verify find_stock_item and get_stock_level work correctly."""
+
+from typing import Optional, Dict, Any
+
+def find_stock_item(data_response: Any) -> Optional[Dict[str, Any]]:
+    """
+    Simulate find_stock_item parsing logic.
+
+    Args:
+        data_response: The response from the API
+
+    Returns:
+        Stock item dictionary or None if not found
+    """
+    data = data_response
+    results = data.get('results', data) if isinstance(data, dict) else data
+    return results[0] if results else None
+
+
+def get_stock_level(item: Optional[Dict[str, Any]]) -> float:
+    """
+    Get stock level from item.
+
+    Args:
+        item: Stock item dictionary
+
+    Returns:
+        Stock quantity
+    """
+    return item.get('quantity', 0) if item else 0
+
+
+# Test cases
+print("Test 1: API returns dict with 'results' key")
+api_response_1 = {
+    'results': [
+        {'pk': 123, 'quantity': 50, 'part': 456, 'location': 789}
+    ]
+}
+item = find_stock_item(api_response_1)
+stock = get_stock_level(item)
+print(f"  Item: {item}")
+print(f"  Stock level: {stock}")
+print(f"  Expected: 50, Got: {stock} - {'PASS' if stock == 50 else 'FAIL'}")
+print()
+
+print("Test 2: API returns dict with empty results")
+api_response_2 = {'results': []}
+item = find_stock_item(api_response_2)
+stock = get_stock_level(item)
+print(f"  Item: {item}")
+print(f"  Stock level: {stock}")
+print(f"  Expected: 0, Got: {stock} - {'PASS' if stock == 0 else 'FAIL'}")
+print()
+
+print("Test 3: API returns list directly")
+api_response_3 = [
+    {'pk': 124, 'quantity': 100, 'part': 456, 'location': 789}
+]
+item = find_stock_item(api_response_3)
+stock = get_stock_level(item)
+print(f"  Item: {item}")
+print(f"  Stock level: {stock}")
+print(f"  Expected: 100, Got: {stock} - {'PASS' if stock == 100 else 'FAIL'}")
+print()
+
+print("Test 4: API returns empty list")
+api_response_4 = []
+item = find_stock_item(api_response_4)
+stock = get_stock_level(item)
+print(f"  Item: {item}")
+print(f"  Stock level: {stock}")
+print(f"  Expected: 0, Got: {stock} - {'PASS' if stock == 0 else 'FAIL'}")
+print()
+
+print("All tests completed!")