chore(frontend): introduce prettier + eslint and prune unused code

- Add Prettier 3 with prettier-plugin-organize-imports (sorts/removes unused imports)
- Add ESLint 10 flat config with typescript-eslint + eslint-plugin-vue + eslint-config-prettier
- Add root scripts: format, format:check, lint, lint:fix
- Reformat 257 files across admin-web, ops-web, desktop-client, packages
- Remove unused locals/exports flagged by --noUnusedLocals/--noUnusedParameters
- Fix duplicate localTabLabel key, surrogate-pair regex u-flag, NBSP literal in regex
- Skip server/ (Go) and apps/browser-extension/ (deprecated per ADR)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/config.yaml

@@ -171,7 +171,7 @@ llm:
 retrieval:
   provider: siliconflow
   base_url: https://api.siliconflow.cn/v1
-  api_key: ‘’ #"sk-dikvcafrdcbajjpfgjjephqcggpdxwxdkighllieijlehwsf"
+  api_key: "sk-dikvcafrdcbajjpfgjjephqcggpdxwxdkighllieijlehwsf"
   embedding_model: BAAI/bge-m3
   reranker_model: BAAI/bge-reranker-v2-m3
   timeout: 30s