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>

pyproject.toml

@@ -0,0 +1,29 @@
+[project]
+name = "stocktool"
+version = "2.0.0"
+description = "InvenTree Stock Management Tool - A comprehensive barcode scanning application for InvenTree inventory management"
+authors = [
+    {name = "InvenTree Stock Tool Contributors"}
+]
+requires-python = ">=3.9"
+dependencies = [
+    "sv-ttk>=2.0.0",
+    "pillow>=10.0.0",
+    "requests>=2.31.0",
+    "pyyaml>=6.0.0",
+]
+readme = "README.md"
+license = {text = "MIT"}
+
+[project.scripts]
+stock-tool = "stocktool.stock_tool_gui_v2:main"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/stocktool"]
+
+[tool.uv]
+dev-dependencies = []