feat(browser-fetch): add lightpanda-backed fetch service and knowledge URL fallback

Adds a new browser-fetch microservice that wraps Lightpanda for rendering
JS-heavy pages, and wires it into the knowledge URL parser as a fallback
when the upstream link reader returns 403/429/5xx for an allow-listed
domain (e.g. zhuanlan.zhihu.com). Includes config/env plumbing, hot-reload
diff support, and full deploy assets (Dockerfile target, docker-compose,
k3s manifests, image-build/package scripts).

deploy/docker-compose.offline.yaml

@@ -18,6 +18,11 @@ services:
     pull_policy: never
     build: !reset null
 
+  browser-fetch:
+    image: geo-rankly/browser-fetch:${IMAGE_TAG:-latest}
+    pull_policy: never
+    build: !reset null
+
   worker-generate:
     image: geo-rankly/worker-generate:${IMAGE_TAG:-latest}
     pull_policy: never