chore(deps): update caddy docker tag to v2.9 (#386)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

frontend/Dockerfile

@@ -7,7 +7,7 @@ RUN npm ci --ignore-scripts && \
     npm run build
 
 # Caddy
-FROM caddy:2.8-alpine
+FROM caddy:2.9-alpine
 
 # Copy static files and config
 COPY --from=build /app/dist /app/dist