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/cmd/server/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"log"
 	"net/http"
 	"os"
@@ -11,14 +12,20 @@ import (
 
 func main() {
 	cfg, err := config.Load(configPath())
-	if err != nil {
+	if err != nil && !errors.Is(err, config.ErrRequireSetup) {
 		log.Fatalf("failed to load config: %v", err)
 	}
 
+	// cfg may be nil when REQUIRE_SETUP — NewServer handles that gracefully.
+	addr := ":4000"
+	if cfg != nil && cfg.ListenAddr != "" {
+		addr = cfg.ListenAddr
+	}
+
 	srv := graph.NewServer(cfg)
 
-	log.Printf("Archivum listening on %s", cfg.ListenAddr)
-	if err := http.ListenAndServe(cfg.ListenAddr, srv); err != nil {
+	log.Printf("Archivum listening on %s", addr)
+	if err := http.ListenAndServe(addr, srv); err != nil {
 		log.Fatal(err)
 	}
 }

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
 }