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/k3s/config/config.yaml

@@ -129,8 +129,8 @@ llm:
   provider: ark
   base_url: https://ark.cn-beijing.volces.com/api/v3
   api_key: "7fb6c66b-129c-4935-9617-709236c4205a"
-  model: doubao-seed-2-0-lite-260215
-  knowledge_url_model: doubao-seed-2-0-mini-260215
+  model: doubao-seed-2-0-pro-260215 # doubao-seed-2-0-lite-260215   #
+  knowledge_url_model: doubao-seed-2-0-mini-260215 #doubao-seed-2-0-mini-260215
   timeout: 2m
   max_output_tokens: 16000
   temperature: 0.7
@@ -172,3 +172,22 @@ generation:
   task_recovery_batch_size: 100
   task_queued_stale_after: 2m
   task_max_attempts: 3
+
+browser_fetch:
+  enabled: true
+  provider: lightpanda
+  service_url: http://browser-fetch:8082
+  queue_size: 64
+  worker_concurrency: 2
+  request_timeout: 45s
+  cache_ttl: 6h
+  allowed_domains:
+    - zhuanlan.zhihu.com
+    - zhihu.com
+  trigger_status:
+    - 403
+    - 429
+    - 500
+    - 502
+    - 503
+    - 504