feat(mcp): serve embedded community MCP server at /mcp

Replace the removed enterprise EE MCP (private apps/server/src/ee submodule,
license-gated /mcp route) with our docmost-mcp, vendored as an isolated ESM
workspace package and served by the server over HTTP — no enterprise license.

Backend:
- Add packages/mcp (@docmost/mcp): vendored docmost-mcp refactored into a
  side-effect-free createDocmostMcpServer() factory (38 tools preserved),
  stdio entry kept in stdio.ts, Streamable-HTTP session manager in http.ts.
- Add apps/server McpModule: @Post/@Get/@Delete('mcp') (served at /mcp via the
  existing global-prefix exclude), @SkipTransform + reply.hijack to bridge raw
  Fastify req/res into the SDK transport. The module dynamically imports the
  ESM-only package from CommonJS via a Function-indirected import resolved with
  require.resolve + file:// URL. Gated by the workspace ai.mcp toggle, a
  service-account (MCP_DOCMOST_EMAIL/PASSWORD/API_URL) and optional MCP_TOKEN;
  per-session idle eviction (MCP_SESSION_IDLE_MS).
- Drop the enterprise license check on mcpEnabled in workspace.service.
- Dockerfile: copy packages/mcp into the production image.
- .env.example: document MCP_DOCMOST_*, MCP_TOKEN, MCP_SESSION_IDLE_MS.

Frontend:
- Recreate the community "AI & MCP" workspace-settings panel (mcp-settings.tsx):
  admin-only toggle on settings.ai.mcp with optimistic update, copyable
  ${APP_URL}/mcp URL; wired into workspace-settings page. Reuses existing i18n.

Fixes:
- Pin packages/mcp tiptap deps to 3.20.4 (matching the client) and inline
  getStyleProperty, preventing a duplicate @tiptap/core@3.26.1 from leaking into
  the client editor via pnpm shamefully-hoist (was breaking apps/client tsc).

apps/server/package.json

@@ -38,6 +38,7 @@
     "@aws-sdk/s3-request-presigner": "3.1050.0",
     "@azure/storage-blob": "12.31.0",
     "@clickhouse/client": "^1.18.2",
+    "@docmost/mcp": "workspace:*",
     "@docmost/pdf-inspector": "1.9.6",
     "@fastify/cookie": "^11.0.2",
     "@fastify/multipart": "^10.0.0",