feat(admin): sessions, staff auth and adminctl

One Redis session store and one cookie for all three identities. Staff
login returns the same error for every failure mode and spends a bcrypt
comparison against a dummy hash when no user exists, so neither the message
nor the timing confirms which addresses have accounts.

Staff users are created only by adminctl. There is no signup endpoint: a
licensing authority that can be joined over the internet is not one.

Pins gin and go-redis to the versions server/ already uses rather than the
latest tidy would pick.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

admin/cmd/adminctl/main.go

@@ -0,0 +1,82 @@
+// Command adminctl performs the operations that deliberately have no HTTP
+// surface.
+//
+//	adminctl staff-add --email=you@example.com --name="You" --password=...
+//
+// There is no staff signup endpoint. A licensing authority that can be joined
+// over the internet is not one.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/mrhid6/vantage/admin/internal/config"
+	"github.com/mrhid6/vantage/admin/internal/db"
+	"github.com/mrhid6/vantage/admin/internal/models"
+	"golang.org/x/crypto/bcrypt"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintln(os.Stderr, "usage: adminctl staff-add")
+		os.Exit(2)
+	}
+
+	cfg, err := config.Load()
+	if err != nil {
+		fatal("configuration: %v", err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	if err := db.Connect(ctx, cfg); err != nil {
+		fatal("database: %v", err)
+	}
+
+	switch os.Args[1] {
+	case "staff-add":
+		staffAdd(ctx, os.Args[2:])
+	default:
+		fmt.Fprintln(os.Stderr, "usage: adminctl staff-add")
+		os.Exit(2)
+	}
+}
+
+func staffAdd(ctx context.Context, args []string) {
+	fs := flag.NewFlagSet("staff-add", flag.ExitOnError)
+	email := fs.String("email", "", "staff email (required)")
+	name := fs.String("name", "", "display name")
+	password := fs.String("password", "", "password, at least 12 characters (required)")
+	fs.Parse(args)
+
+	if *email == "" || len(*password) < 12 {
+		fatal("--email and a --password of at least 12 characters are required")
+	}
+
+	hash, err := bcrypt.GenerateFromPassword([]byte(*password), 12)
+	if err != nil {
+		fatal("hash: %v", err)
+	}
+
+	u := models.StaffUser{
+		UserID:       uuid.NewString(),
+		Email:        strings.ToLower(strings.TrimSpace(*email)),
+		PasswordHash: string(hash),
+		Name:         *name,
+		CreatedAt:    time.Now().UTC(),
+	}
+	if _, err := db.Admin("staff_users").InsertOne(ctx, u); err != nil {
+		fatal("create staff user: %v", err)
+	}
+	fmt.Printf("created staff user %s\n", u.Email)
+}
+
+func fatal(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, format+"\n", a...)
+	os.Exit(1)
+}

admin/cmd/main.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/joho/godotenv"
+	"github.com/mrhid6/vantage/admin/internal/auth"
 	"github.com/mrhid6/vantage/admin/internal/config"
 	"github.com/mrhid6/vantage/admin/internal/db"
 	"github.com/mrhid6/vantage/admin/internal/inject"
@@ -28,6 +29,14 @@ func main() {
 
 	licensing.SetSigningKey(cfg.SigningKey)
 
+	auth.InitRedis(cfg.RedisAddr)
+	pingCtx, pingCancel := context.WithTimeout(context.Background(), 10*time.Second)
+	if err := auth.Ping(pingCtx); err != nil {
+		pingCancel()
+		log.Fatalf("redis: %v", err)
+	}
+	pingCancel()
+
 	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
 	if err := db.Connect(ctx, cfg); err != nil {
 		cancel()