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.yaml

@@ -16,6 +16,7 @@ x-app-env: &app-env
   JWT_ACCESS_TTL: ${JWT_ACCESS_TTL:-15m}
   JWT_REFRESH_TTL: ${JWT_REFRESH_TTL:-720h}
   SCHEDULER_INTERNAL_METRICS_TOKEN: ${SCHEDULER_INTERNAL_METRICS_TOKEN:-}
+  BROWSER_FETCH_TOKEN: ${BROWSER_FETCH_TOKEN:-}
   OBJECT_STORAGE_ACCESS_KEY: ${MINIO_ROOT_USER:-minioadmin}
   OBJECT_STORAGE_SECRET_KEY: ${MINIO_ROOT_PASSWORD:-minioadmin}
 
@@ -261,6 +262,33 @@ services:
       retries: 5
       start_period: 10s
 
+  browser-fetch:
+    image: ${IMAGE_REGISTRY:-ghcr.io/your-org/geo-rankly}/browser-fetch:${IMAGE_TAG:-latest}
+    container_name: geo-browser-fetch
+    build:
+      context: ../server
+      dockerfile: Dockerfile
+      target: browser-fetch
+      args:
+        SERVICE: browser-fetch
+    restart: unless-stopped
+    environment:
+      BROWSER_FETCH_TOKEN: ${BROWSER_FETCH_TOKEN:-geo-browser-fetch-change-me}
+      BROWSER_FETCH_ALLOWED_DOMAINS: zhuanlan.zhihu.com,zhihu.com
+      BROWSER_FETCH_QUEUE_SIZE: 128
+      BROWSER_FETCH_WORKER_CONCURRENCY: 2
+      BROWSER_FETCH_PER_DOMAIN_CONCURRENCY: 1
+      BROWSER_FETCH_REQUEST_TIMEOUT: 45s
+      BROWSER_FETCH_CACHE_TTL: 6h
+      LIGHTPANDA_DRIVER: fetch
+      LIGHTPANDA_FETCH_ARGS: --dump markdown
+    healthcheck:
+      test: ["/app/service", "-healthcheck"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 10s
+
   worker-generate:
     image: ${IMAGE_REGISTRY:-ghcr.io/your-org/geo-rankly}/worker-generate:${IMAGE_TAG:-latest}
     container_name: geo-worker-generate