feat(agents): consolidate connectors under mcp_discovery; route web search through google_search

MCP consolidation:
- Route all MCP-capable connectors (Slack, Jira, Linear, ClickUp, Airtable,
  Notion, Confluence, interim Gmail/Calendar, custom MCP) through a single
  `mcp_discovery` subagent. Drive/OneDrive/Dropbox stay native to enrich the KB.
- Deprecate Discord/Teams/Luma: no viable official MCP server.

Google-only web search:
- Remove the main-agent `web_search` tool and the SearXNG platform service;
  all public web search now flows through the `google_search` subagent via task().
- Deprecate the Tavily/SearXNG/Linkup/Baidu search connectors (HTTP 410 on
  create, "Deprecated" badge); guide heavy users to the custom MCP connector.
- Remove web search from anonymous chat (pure Q&A).
- Tear SearXNG out of docker compose + install scripts; drop tavily-python
  and linkup-sdk deps and their config/env vars.

Fix:
- metrics._package_version() now swallows any metadata lookup failure. A
  malformed editable-install distribution with no `Version` field raised
  KeyError deep in importlib.metadata, and since it runs on every
  record_subagent_invoke_duration call it was crashing every task()
  delegation. Verified end-to-end against live GPT-5.4.

Co-authored-by: Cursor <cursoragent@cursor.com>

surfsense_web/messages/zh.json

@@ -335,7 +335,6 @@
 	"add_connector": {
 		"title": "连接您的工具",
 		"subtitle": "集成您喜欢的服务以增强研究能力。",
-		"web_search": "网络搜索",
 		"messaging": "即时通讯",
 		"project_management": "项目管理",
 		"documentation": "文档协作",
@@ -758,27 +757,7 @@
 		"general_reset": "重置更改",
 		"general_save": "保存更改",
 		"general_saving": "保存中...",
-		"general_unsaved_changes": "您有未保存的更改。点击\"保存更改\"以应用它们。",
-		"nav_web_search": "网页搜索",
-		"nav_web_search_desc": "内置网页搜索设置",
-		"web_search_title": "网页搜索",
-		"web_search_description": "网页搜索由内置 SearXNG 实例提供支持。所有查询都通过您的服务器代理；不会向第三方发送数据。",
-		"web_search_enabled_label": "启用网页搜索",
-		"web_search_enabled_description": "启用后，AI 代理可以搜索网页以获取新闻、价格和当前事件等实时信息。",
-		"web_search_status_healthy": "网页搜索服务运行正常",
-		"web_search_status_unhealthy": "网页搜索服务不可用",
-		"web_search_status_not_configured": "网页搜索服务未配置",
-		"web_search_engines_label": "搜索引擎",
-		"web_search_engines_placeholder": "google,brave,duckduckgo",
-		"web_search_engines_description": "要使用的 SearXNG 引擎的逗号分隔列表。留空则使用默认值。",
-		"web_search_language_label": "首选语言",
-		"web_search_language_placeholder": "zh",
-		"web_search_language_description": "IETF 语言标签（例如 zh、zh-CN）。留空则自动检测。",
-		"web_search_safesearch_label": "SafeSearch 级别",
-		"web_search_safesearch_description": "0 = 关闭，1 = 中等，2 = 严格",
-		"web_search_save": "保存网页搜索设置",
-		"web_search_saving": "保存中...",
-		"web_search_saved": "网页搜索设置已保存"
+		"general_unsaved_changes": "您有未保存的更改。点击\"保存更改\"以应用它们。"
 	},
 	"homepage": {
 		"hero_title_part1": "AI 工作空间",