feat: add gateway bootstrap endpoint with token-based authentication

Add Bootstrap and AgentSyncBundle handlers to gateway package with X-Gateway-Bootstrap-Token header authentication. Implement UpsertByName repository method for idempotent gateway registration. Update gateway entrypoint script to auto-generate keys and bootstrap gateway on first run, persisting gateway ID to disk. Add GATEWAY_BOOTSTRAP_TOKEN config and update environment variables for gateway name, bootstrap URL, and sync URL.

backend/internal/gateway/handler.go

@@ -10,11 +10,12 @@ import (
 )
 
 type Handler struct {
-	service *Service
+	service        *Service
+	bootstrapToken string
 }
 
-func NewHandler(service *Service) *Handler {
-	return &Handler{service: service}
+func NewHandler(service *Service, bootstrapToken string) *Handler {
+	return &Handler{service: service, bootstrapToken: bootstrapToken}
 }
 
 func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
@@ -52,3 +53,39 @@ func (h *Handler) Update(w http.ResponseWriter, r *http.Request) {
 
 	apiutil.JSON(w, http.StatusOK, item)
 }
+
+func (h *Handler) Bootstrap(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("X-Gateway-Bootstrap-Token") != h.bootstrapToken {
+		apiutil.Error(w, http.StatusUnauthorized, "unauthorized", "invalid gateway bootstrap token")
+		return
+	}
+
+	var input BootstrapRequest
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "invalid_json", "invalid request body")
+		return
+	}
+
+	item, err := h.service.Bootstrap(r.Context(), input)
+	if err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "gateway_bootstrap_failed", "unable to bootstrap gateway")
+		return
+	}
+
+	apiutil.JSON(w, http.StatusOK, item)
+}
+
+func (h *Handler) AgentSyncBundle(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("X-Gateway-Bootstrap-Token") != h.bootstrapToken {
+		apiutil.Error(w, http.StatusUnauthorized, "unauthorized", "invalid gateway bootstrap token")
+		return
+	}
+
+	bundle, err := h.service.BuildSyncBundle(r.Context(), chi.URLParam(r, "id"))
+	if err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "gateway_sync_failed", "unable to build sync bundle")
+		return
+	}
+
+	apiutil.JSON(w, http.StatusOK, bundle)
+}

backend/internal/gateway/repository.go

@@ -15,6 +15,7 @@ type Repository interface {
 	FirstActive(ctx context.Context) (Gateway, error)
 	BuildSyncBundle(ctx context.Context, gatewayID uuid.UUID) (wireguard.GatewayBundle, error)
 	Update(ctx context.Context, gatewayID uuid.UUID, input UpdateRequest) (Gateway, error)
+	UpsertByName(ctx context.Context, input BootstrapRequest) (Gateway, error)
 }
 
 type PGRepository struct {
@@ -136,6 +137,27 @@ func (r *PGRepository) Update(ctx context.Context, gatewayID uuid.UUID, input Up
 	return item, err
 }
 
+func (r *PGRepository) UpsertByName(ctx context.Context, input BootstrapRequest) (Gateway, error) {
+	row := r.db.QueryRow(ctx, `
+		insert into gateways (id, name, endpoint, public_key, listen_port, vpn_cidr, dns_servers, is_active)
+		values ($1, $2, $3, $4, $5, $6::cidr, $7::text[], true)
+		on conflict (name)
+		do update set
+			endpoint = excluded.endpoint,
+			public_key = excluded.public_key,
+			listen_port = excluded.listen_port,
+			vpn_cidr = excluded.vpn_cidr,
+			dns_servers = excluded.dns_servers,
+			is_active = true,
+			updated_at = now()
+		returning id, name, endpoint, public_key, listen_port, vpn_cidr::text, dns_servers, is_active
+	`, uuid.New(), input.Name, input.Endpoint, input.PublicKey, input.ListenPort, input.VPNCIDR, input.DNSServers)
+
+	var item Gateway
+	err := row.Scan(&item.ID, &item.Name, &item.Endpoint, &item.PublicKey, &item.ListenPort, &item.VPNCIDR, &item.DNSServers, &item.IsActive)
+	return item, err
+}
+
 func gatewayInterfaceAddress(cidr string) (string, error) {
 	prefix, err := netip.ParsePrefix(cidr)
 	if err != nil {

backend/internal/gateway/service.go

@@ -39,3 +39,19 @@ func (s *Service) Update(ctx context.Context, gatewayID string, input UpdateRequ
 	}
 	return s.repo.Update(ctx, id, input)
 }
+
+func (s *Service) Bootstrap(ctx context.Context, input BootstrapRequest) (Gateway, error) {
+	if input.Name == "" {
+		input.Name = "primary-gateway"
+	}
+	if input.ListenPort == 0 {
+		input.ListenPort = 51820
+	}
+	if input.VPNCIDR == "" {
+		input.VPNCIDR = "100.96.0.0/24"
+	}
+	if len(input.DNSServers) == 0 {
+		input.DNSServers = []string{"10.20.0.53"}
+	}
+	return s.repo.UpsertByName(ctx, input)
+}

backend/internal/gateway/types.go

@@ -21,3 +21,12 @@ type UpdateRequest struct {
 	DNSServers []string `json:"dns_servers"`
 	IsActive   bool     `json:"is_active"`
 }
+
+type BootstrapRequest struct {
+	Name       string   `json:"name"`
+	Endpoint   string   `json:"endpoint"`
+	PublicKey  string   `json:"public_key"`
+	ListenPort int      `json:"listen_port"`
+	VPNCIDR    string   `json:"vpn_cidr"`
+	DNSServers []string `json:"dns_servers"`
+}