Minimal API for config-by-host and builder state. Version 0.1.0.
GET /api/config — Client config by Host header (or ?host=). Returns 404 if no workspace is associated with that host.GET /api/builder/state — Load builder state (requires X-User-Id or Authorization header).PUT /api/builder/state — Save builder state (requires X-User-Id or Authorization; body: { state, selectedWorkspaceIndex }).