main.go no longer fatals on ErrRequireSetup — it passes cfg=nil to NewServer.
NewServer returns REQUIRE_SETUP on every GraphQL call when cfg is nil, and
also adds CORS headers and serves the Vue SPA from /srv/archivum/ui.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Removed go.sum from the COPY cache layer — go mod download -x creates it
when absent. Added empty backend/go.sum for local tooling (gopls, go build).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>