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>

docker/docker-compose.yml

@@ -81,19 +81,6 @@ services:
   #     timeout: 5s
   #     retries: 3
 
-  searxng:
-    image: searxng/searxng:2026.3.13-3c1f68c59
-    volumes:
-      - ./searxng:/etc/searxng
-    environment:
-      SEARXNG_SECRET: ${SEARXNG_SECRET:-surfsense-searxng-secret}
-    restart: unless-stopped
-    healthcheck:
-      test: ["CMD", "wget", "--spider", "-q", "http://localhost:8080/healthz"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-
   # Single public entry point for the Docker stack. Comment this service out
   # only if you front SurfSense with your own reverse proxy.
   proxy:
@@ -146,7 +133,6 @@ services:
       FILE_STORAGE_LOCAL_PATH: /app/.local_object_store
       NEXT_FRONTEND_URL: ${NEXT_FRONTEND_URL:-${SURFSENSE_PUBLIC_URL:-http://localhost:${LISTEN_HTTP_PORT:-3929}}}
       BACKEND_URL: ${BACKEND_URL:-${SURFSENSE_PUBLIC_URL:-http://localhost:${LISTEN_HTTP_PORT:-3929}}}
-      SEARXNG_DEFAULT_HOST: ${SEARXNG_DEFAULT_HOST:-http://searxng:8080}
       WHATSAPP_BRIDGE_URL: ${WHATSAPP_BRIDGE_URL:-http://whatsapp-bridge:9929}
       # Daytona Sandbox – uncomment and set credentials to enable cloud code execution
       # DAYTONA_SANDBOX_ENABLED: "TRUE"
@@ -161,8 +147,6 @@ services:
         condition: service_healthy
       redis:
         condition: service_healthy
-      searxng:
-        condition: service_healthy
       migrations:
         condition: service_completed_successfully
     restart: unless-stopped
@@ -210,7 +194,6 @@ services:
       CELERY_TASK_DEFAULT_QUEUE: surfsense
       PYTHONPATH: /app
       FILE_STORAGE_LOCAL_PATH: /app/.local_object_store
-      SEARXNG_DEFAULT_HOST: ${SEARXNG_DEFAULT_HOST:-http://searxng:8080}
       SERVICE_ROLE: worker
     depends_on:
       db: