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/en.json

@@ -336,7 +336,6 @@
 	"add_connector": {
 		"title": "Connect Your Tools",
 		"subtitle": "Integrate with your favorite services to enhance your research capabilities.",
-		"web_search": "Web Search",
 		"messaging": "Messaging",
 		"project_management": "Project Management",
 		"documentation": "Documentation",
@@ -759,27 +758,7 @@
 		"general_reset": "Reset Changes",
 		"general_save": "Save Changes",
 		"general_saving": "Saving",
-		"general_unsaved_changes": "You have unsaved changes. Click \"Save Changes\" to apply them.",
-		"nav_web_search": "Web Search",
-		"nav_web_search_desc": "Built-in web search settings",
-		"web_search_title": "Web Search",
-		"web_search_description": "Web search is powered by a built-in SearXNG instance. All queries are proxied through your server — no data is sent to third parties.",
-		"web_search_enabled_label": "Enable Web Search",
-		"web_search_enabled_description": "When enabled, the AI agent can search the web for real-time information like news, prices, and current events.",
-		"web_search_status_healthy": "Web search service is healthy",
-		"web_search_status_unhealthy": "Web search service is unavailable",
-		"web_search_status_not_configured": "Web search service is not configured",
-		"web_search_engines_label": "Search Engines",
-		"web_search_engines_placeholder": "google,brave,duckduckgo",
-		"web_search_engines_description": "Comma-separated list of SearXNG engines to use. Leave empty for defaults.",
-		"web_search_language_label": "Preferred Language",
-		"web_search_language_placeholder": "en",
-		"web_search_language_description": "IETF language tag (e.g. en, en-US). Leave empty for auto-detect.",
-		"web_search_safesearch_label": "SafeSearch Level",
-		"web_search_safesearch_description": "0 = off, 1 = moderate, 2 = strict",
-		"web_search_save": "Save Web Search Settings",
-		"web_search_saving": "Saving...",
-		"web_search_saved": "Web search settings saved"
+		"general_unsaved_changes": "You have unsaved changes. Click \"Save Changes\" to apply them."
 	},
 	"homepage": {
 		"hero_title_part1": "The AI Workspace",