chore: CI/build improvements and version detection

- Rename GITEA_TOKEN to DEPLOY_TOKEN in release workflow
- Extract shared version detection into build-common.sh
- Use importlib.metadata for runtime version instead of hardcoded string
- Use PEP 440 parsing (packaging lib) for update version comparison
- Add packaging>=23.0 to dependencies
- Fix update banner close button alignment (CSS)
- Update CLAUDE.md with versioning docs and frontend rebuild notes

media_server/__init__.py

@@ -1,3 +1,23 @@
 """Media Server - REST API for controlling system media playback."""
 
-__version__ = "1.0.1"
+from importlib.metadata import PackageNotFoundError, version
+from pathlib import Path
+
+
+def _detect_version() -> str:
+    # 1. Package metadata (works when pip-installed in dev)
+    try:
+        return version("media-server")
+    except PackageNotFoundError:
+        pass
+
+    # 2. VERSION file written by build scripts (production builds)
+    # Located at install root, two levels up from this package
+    version_file = Path(__file__).resolve().parent.parent.parent / "VERSION"
+    if version_file.is_file():
+        return version_file.read_text().strip()
+
+    return "0.0.0-dev"
+
+
+__version__ = _detect_version()