refactor: serve MCP bundles under <name>/mcp with nginx guard; rename core->mcp_server

- collect.py: copy repo MCP bundles to ROOT/<name>/mcp (instead of ROOT/mcp/<name>); add nginx location guard to deny /<name>/mcp/
- config.py: bundle roots now point to <repo>/mcp and standards/mcp for static bundles
- Rename core.py -> mcp_server.py and update imports in main.py and registry.py
- Dockerfile: per-repo MCP COPYs under /app/<name>/mcp, drop blog copy; add ports 8008/8009 in .drone.yml
- Restore standards/mcp/libraries.json from git for registry server

config.py

@@ -39,7 +39,7 @@ class ServiceConfig:
         """Return every MCP server: one per repo that declares a bundle, plus
         the hand-authored static servers (for example the standards registry)."""
         servers: dict[str, MCPBundle] = {
-            r.name: MCPBundle(root=Path("mcp") / r.name, name=r.mcp_server, port=r.mcp_port)
+            r.name: MCPBundle(root=Path(r.name) / "mcp", name=r.mcp_server, port=r.mcp_port)
             for r in self.repos
             if r.mcp_port is not None
         }