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.dev.yml

@@ -85,20 +85,6 @@ services:
       - "${OTEL_TEMPO_PORT:-3200}:3200"
     restart: unless-stopped
 
-  searxng:
-    image: searxng/searxng:2026.3.13-3c1f68c59
-    ports:
-      - "${SEARXNG_PORT:-8888}:8080"
-    volumes:
-      - ./searxng:/etc/searxng
-    environment:
-      - SEARXNG_SECRET=${SEARXNG_SECRET:-surfsense-searxng-secret}
-    healthcheck:
-      test: ["CMD", "wget", "--spider", "-q", "http://localhost:8080/healthz"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-
   backend:
     build: *backend-build
     ports:
@@ -125,7 +111,6 @@ services:
       - LANGSMITH_TRACING=false
       - AUTH_TYPE=${AUTH_TYPE:-LOCAL}
       - NEXT_FRONTEND_URL=${NEXT_FRONTEND_URL:-http://localhost:3000}
-      - 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
@@ -138,8 +123,6 @@ services:
         condition: service_healthy
       redis:
         condition: service_healthy
-      searxng:
-        condition: service_healthy
       migrations:
         condition: service_completed_successfully
     healthcheck:
@@ -186,7 +169,6 @@ 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: