Add register-by-signature, web fixes, bin scripts, docs

- Register by signing service key: GET /v1/service-key, POST /v1/auth/register-by-signature
- Login auto-attempts register first for new users
- Web: default API URL momswap.produktor.duckdns.org, /libs/ static handler
- Docker: webbuild stage for geo-api-client, copy web+libs to runtime
- Bin scripts: test.sh, run.sh, up.sh, down.sh
- docs/ed25519-security-use-cases.md: use cases, message formats, examples
- SERVICE_PUBLIC_KEY env (defaults to ADMIN_PUBLIC_KEY)

Made-with: Cursor

cmd/api/main.go

@@ -14,12 +14,13 @@ import (
 func main() {
 	addr := getEnv("ADDR", ":8122")
 	adminPublicKey := os.Getenv("ADMIN_PUBLIC_KEY")
+	servicePublicKey := getEnv("SERVICE_PUBLIC_KEY", adminPublicKey)
 
 	memory := store.NewMemoryStore()
 	service := app.NewService(memory, app.Config{
 		ChallengeTTL: 5 * time.Minute,
 		SessionTTL:   24 * time.Hour,
-	})
+	}, servicePublicKey)
 	service.BootstrapAdmin(adminPublicKey)
 
 	api := httpapi.NewAPI(service)