feat(settings): add MCP registrations endpoint + Coolify volume runbook

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/app.py

@@ -2818,6 +2818,13 @@ async def api_mcp_tools():
     return {"tools": tools, "count": len(tools)}
 
 
+@app.get("/api/settings/mcp/registrations")
+async def api_mcp_registrations():
+    """List MCP server registrations from host config files."""
+    from web.mcp_registrations import list_registrations
+    return list_registrations()
+
+
 # ── Settings: Tag → Company Mappings ──────────────────────────────
 
 @app.get("/api/settings/paperclip-companies")