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

CLAUDE.md

@@ -41,10 +41,20 @@ Unregister-ScheduledTask -TaskName "MediaServer" -Confirm:$false
 
 **When restart is NOT needed:**
 
-- Static file changes (`*.html`, `*.css`, `*.js`, `*.json`) - browser refresh is enough
+- Static file changes (`*.html`, `*.css`, `*.json`) - browser refresh is enough
 - README or documentation updates
 - Changes to install/service scripts (only affects new installations)
 
+### Frontend Rebuild After JS Changes
+
+**CRITICAL:** The frontend is bundled via esbuild into `static/dist/app.bundle.js`. After modifying ANY JavaScript file in `media_server/static/js/`, you **MUST** run:
+
+```bash
+npm run build
+```
+
+Raw JS file edits have **NO effect** until the bundle is rebuilt. After rebuilding, a browser hard-refresh (Ctrl+Shift+R) is sufficient — no server restart needed.
+
 **How to restart during development:**
 
 1. Find the running server process:
@@ -124,12 +134,17 @@ To add support for a new language:
 
 ## Versioning
 
-Version is tracked in two files that must be kept in sync:
+**`pyproject.toml`** is the single source of truth for the version string.
 
-- `pyproject.toml` - `[project].version`
-- `media_server/__init__.py` - `__version__`
+At runtime, `media_server/__init__.py` reads the version via `importlib.metadata.version()` — no manual syncing needed.
 
-When releasing a new version, update both files with the same version string.
+Version flow:
+1. `git tag v0.3.0` → CI reads the tag
+2. Build scripts stamp `pyproject.toml` with the clean version via `sed`
+3. `pip install` bakes the version into package metadata
+4. `importlib.metadata.version("media-server")` reads it at runtime
+
+When bumping the version for a new release, only `pyproject.toml` needs to be updated.
 
 **Important:** After making any changes, always ask the user if the version needs to be incremented.