feat: add version display to frontend and /api/version endpoint (v1.2.5)

- Add GET /api/version endpoint that reads VERSION file
- Frontend fetches version on init and displays it as a badge in the header
- Add version-badge CSS styling
- Update docker-compose.yml comment to v1.2.5

backend/main.py

@@ -134,6 +134,12 @@ async def metrics():
     return Response(content=prometheus_metrics(), media_type="text/plain")
 
 
+@app.get("/api/version")
+async def version():
+    version_file = Path(__file__).parent.parent / "VERSION"
+    return {"version": version_file.read_text().strip() if version_file.exists() else "unknown"}
+
+
 frontend_dir = Path(__file__).parent / "frontend"
 app.mount("/", StaticFiles(directory=frontend_dir, html=True), name="frontend")