chore: add Context7 MCP server for library docs

Checked docs/research for more useful MCP servers beyond leankg/
codebase-memory-mcp/playwright. Added Context7 (@upstash/context7-mcp,
61.5K stars, official Upstash) via npx — live docs lookup for the
libraries this project actually pulls in (sabre/dav, sabre/vobject,
laminas-feed, endroid/qr-code, FullCalendar, Vite, Symfony), none of
which have an offline index the way msgraph does for Graph.

Evaluated and rejected CalDAV/Nextcloud MCP servers (caldav-mcp 98
stars, aiquila-mcp 34 stars — real but too young, and would need a
live Nextcloud app-password before any account is even provisioned)
and Gitea MCP servers (0-1 stars, redundant with the tea CLI already
standardized on via the gitea-tea skill). No Docker MCP found as an
installable package — Docker's own MCP tooling lives inside Docker
Desktop's MCP Toolkit, not npm/pip, and there's no Dockerfile/CI yet
to make it relevant.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tu1c13iVNdj1iWL633yazG

.mcp.json

@@ -10,6 +10,10 @@
     "playwright": {
       "command": "npx",
       "args": ["-y", "@playwright/mcp@latest"]
+    },
+    "context7": {
+      "command": "npx",
+      "args": ["-y", "@upstash/context7-mcp@latest"]
     }
   }
 }