fix: server starts even without config (REQUIRE_SETUP mode)

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>

backend/internal/graph/server.go

@@ -7,22 +7,38 @@ import (
 )
 
 // NewServer wires up the HTTP handler for the GraphQL endpoint.
-// Replace the stub handler with the gqlgen-generated handler once
-// `go generate ./...` has been run.
+// cfg may be nil when the system has not been configured yet; in that case
+// every GraphQL request returns {"data":{"systemStatus":"REQUIRE_SETUP"}} so
+// the frontend can redirect to the Setup Wizard.
 func NewServer(cfg *config.Config) http.Handler {
 	mux := http.NewServeMux()
 
-	// Placeholder — replace with generated gqlgen handler.
 	mux.HandleFunc("/graphql", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusNoContent)
+			return
+		}
+
+		if cfg == nil {
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(`{"data":{"systemStatus":"REQUIRE_SETUP"}}`))
+			return
+		}
+
+		// TODO: replace with gqlgen handler once generated.
 		w.WriteHeader(http.StatusOK)
-		_, _ = w.Write([]byte(`{"data":{"systemStatus":"REQUIRE_SETUP"}}`))
+		_, _ = w.Write([]byte(`{"data":{"systemStatus":"OK"}}`))
 	})
 
-	// Simple health check.
 	mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
 	})
 
+	// Serve the embedded Vue SPA for every other path.
+	mux.Handle("/", http.FileServer(http.Dir("/srv/archivum/ui")))
+
 	return mux
 }