feat: add version management with setuptools-scm

- Configure hatch-vcs for automatic version generation from git tags
- Update pyproject.toml to use dynamic versioning
- Add src/_version.py for runtime version access
- Update src/__init__.py to import version from _version
- Add __APP_VERSION__ to frontend vite config
- Add version script to frontend package.json
- Update CI workflows to trigger on version tags instead of branches

src/__init__.py

@@ -7,5 +7,10 @@ from dotenv import load_dotenv
 
 # Load environment variables from .env file
 load_dotenv()
-__version__ = "9.1.0"
+
+try:
+    from src._version import __version__
+except ImportError:
+    __version__ = "0.0.0.dev0"
+
 __author__ = "AI Proxy"