feat(invites): team invite links — admin create/revoke, public accept (#42)

* feat(branding): white-label — public /branding, admin write, shell theming

app_settings branding.* keys (product name, logo/favicon URLs, accent
color, docs/support links). Public GET /branding so login and shell
theme pre-auth; admin writes via PUT /settings.

useBranding() applies document.title, accent CSS var and favicon;
BrandWordmark replaces hardcoded wordmarks; admin Platform settings
gain a Branding form. MCP containr_branding_get + settings_update.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(invites): team invite links — admin create/revoke, public accept

Admins mint single-use invite links (sha256-hashed token at rest,
optional email binding, configurable TTL). Public endpoints let the
accept page validate the link and register — working even while
public signup is disabled.

- migration + sqlc queries/model for user_invites
- POST /admin/invites (returns one-time token+url), GET list, DELETE revoke
- GET /auth/invites/:token public validation, POST /auth/accept-invite
- CLI containr invites list|create|revoke; MCP invites tools
- /auth/accept-invite page (expired/used/invalid states, bound-email lock)
- Admin page Team invites section: create, copy link, revoke
- OpenAPI + generated types + CLI guide

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/invites.go

@@ -0,0 +1,245 @@
+package api
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"database/sql"
+	"encoding/hex"
+	"errors"
+	"net/http"
+	"strings"
+	"time"
+
+	"containr/internal/database"
+	"containr/internal/database/sqlcdb"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"golang.org/x/crypto/bcrypt"
+)
+
+// Team invites: an admin creates a single-use link; the invitee registers
+// through it even while public signup is closed. Tokens are random 32-byte
+// values shared once — only their sha256 hash is stored.
+
+type inviteJSON struct {
+	ID        string     `json:"id"`
+	Email     *string    `json:"email,omitempty"`
+	ExpiresAt time.Time  `json:"expires_at"`
+	UsedAt    *time.Time `json:"used_at,omitempty"`
+	CreatedAt *time.Time `json:"created_at,omitempty"`
+}
+
+func toInviteJSON(i sqlcdb.UserInvite) inviteJSON {
+	out := inviteJSON{ID: i.ID.String(), ExpiresAt: i.ExpiresAt}
+	if i.Email.Valid && i.Email.String != "" {
+		out.Email = &i.Email.String
+	}
+	if i.UsedAt.Valid {
+		out.UsedAt = &i.UsedAt.Time
+	}
+	if i.CreatedAt.Valid {
+		out.CreatedAt = &i.CreatedAt.Time
+	}
+	return out
+}
+
+func inviteTokenHash(token string) string {
+	sum := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(sum[:])
+}
+
+func generateInviteToken() (string, error) {
+	buf := make([]byte, 32)
+	if _, err := rand.Read(buf); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(buf), nil
+}
+
+// POST /admin/invites — {email?, expires_in_hours?} → {invite, token, url}
+func handleAdminCreateInvite(c *gin.Context) {
+	var req struct {
+		Email          string `json:"email"`
+		ExpiresInHours *int   `json:"expires_in_hours"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		respondError(c, http.StatusBadRequest, "INVALID_BODY", "invalid request body")
+		return
+	}
+	ttl := 24 * 7
+	if req.ExpiresInHours != nil {
+		if *req.ExpiresInHours < 1 || *req.ExpiresInHours > 24*90 {
+			respondError(c, http.StatusBadRequest, "VALIDATION", "expires_in_hours must be 1–2160")
+			return
+		}
+		ttl = *req.ExpiresInHours
+	}
+	token, err := generateInviteToken()
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to generate token")
+		return
+	}
+	userID, _ := requireAuthenticatedUserUUID(c)
+	params := sqlcdb.CreateUserInviteParams{
+		TokenHash: inviteTokenHash(token),
+		CreatedBy: uuid.NullUUID{UUID: userID, Valid: true},
+		ExpiresAt: time.Now().UTC().Add(time.Duration(ttl) * time.Hour),
+	}
+	if email := strings.ToLower(strings.TrimSpace(req.Email)); email != "" {
+		params.Email = sql.NullString{String: email, Valid: true}
+	}
+	db := c.MustGet("db").(*database.DB)
+	invite, err := sqlcdb.New(db.DB).CreateUserInvite(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to create invite")
+		return
+	}
+	c.JSON(http.StatusCreated, gin.H{
+		"invite": toInviteJSON(invite),
+		"token":  token,
+		"url":    "/auth/accept-invite?token=" + token,
+	})
+}
+
+// GET /admin/invites
+func handleAdminListInvites(c *gin.Context) {
+	db := c.MustGet("db").(*database.DB)
+	invites, err := sqlcdb.New(db.DB).ListUserInvites(c.Request.Context())
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to list invites")
+		return
+	}
+	out := make([]inviteJSON, 0, len(invites))
+	for _, i := range invites {
+		out = append(out, toInviteJSON(i))
+	}
+	c.JSON(http.StatusOK, gin.H{"invites": out})
+}
+
+// DELETE /admin/invites/:id — revoke an unused invite.
+func handleAdminDeleteInvite(c *gin.Context) {
+	id, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, http.StatusBadRequest, "INVALID_ID", "invalid invite id")
+		return
+	}
+	db := c.MustGet("db").(*database.DB)
+	if err := sqlcdb.New(db.DB).DeleteUserInvite(c.Request.Context(), id); err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to delete invite")
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// GET /auth/invites/:token — public. Lets the accept page validate the link
+// and pre-fill a bound email before the user commits to registering.
+func handleGetInvite(c *gin.Context) {
+	db := c.MustGet("db").(*database.DB)
+	invite, err := sqlcdb.New(db.DB).GetUserInviteByTokenHash(c.Request.Context(), inviteTokenHash(c.Param("token")))
+	if err != nil {
+		respondError(c, http.StatusNotFound, "NOT_FOUND", "invite not found")
+		return
+	}
+	expired := time.Now().After(invite.ExpiresAt)
+	var email *string
+	if invite.Email.Valid && invite.Email.String != "" {
+		email = &invite.Email.String
+	}
+	c.JSON(http.StatusOK, gin.H{
+		"valid":      !invite.UsedAt.Valid && !expired,
+		"used":       invite.UsedAt.Valid,
+		"expired":    expired,
+		"email":      email,
+		"expires_at": invite.ExpiresAt,
+	})
+}
+
+// POST /auth/accept-invite — {token, name, email, password}
+func handleAcceptInvite(c *gin.Context) {
+	var req struct {
+		Token    string `json:"token" binding:"required"`
+		Name     string `json:"name" binding:"required"`
+		Email    string `json:"email" binding:"required"`
+		Password string `json:"password" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		respondError(c, http.StatusBadRequest, "INVALID_BODY", "token, name, email and password are required")
+		return
+	}
+	if len(req.Password) < 8 {
+		respondError(c, http.StatusBadRequest, "VALIDATION", "password must be at least 8 characters")
+		return
+	}
+	req.Email = strings.ToLower(strings.TrimSpace(req.Email))
+
+	db := c.MustGet("db").(*database.DB)
+	q := sqlcdb.New(db.DB)
+	invite, err := q.GetUserInviteByTokenHash(c.Request.Context(), inviteTokenHash(req.Token))
+	if err != nil {
+		respondError(c, http.StatusNotFound, "NOT_FOUND", "invite not found")
+		return
+	}
+	if invite.UsedAt.Valid {
+		respondError(c, http.StatusGone, "INVITE_USED", "invite already used")
+		return
+	}
+	if time.Now().After(invite.ExpiresAt) {
+		respondError(c, http.StatusGone, "INVITE_EXPIRED", "invite expired")
+		return
+	}
+	if invite.Email.Valid && invite.Email.String != "" && invite.Email.String != req.Email {
+		respondError(c, http.StatusForbidden, "INVITE_EMAIL_MISMATCH", "invite is bound to a different email")
+		return
+	}
+
+	var existing int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM users WHERE email = $1`, req.Email).Scan(&existing); err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "database error")
+		return
+	}
+	if existing > 0 {
+		respondError(c, http.StatusConflict, "CONFLICT", "user already exists")
+		return
+	}
+
+	if err := createBetterAuthUser(c, strings.TrimSpace(req.Name), req.Email, req.Password); err != nil && !errors.Is(err, errBetterAuthUserExists) {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", err.Error())
+		return
+	}
+
+	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.Password), bcrypt.DefaultCost)
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to hash password")
+		return
+	}
+
+	var user User
+	err = db.QueryRow(`
+		INSERT INTO users (email, password_hash, name)
+		VALUES ($1, $2, $3)
+		RETURNING id, email, name, COALESCE(avatar_url, ''), is_admin, created_at
+	`, req.Email, string(hashedPassword), strings.TrimSpace(req.Name)).
+		Scan(&user.ID, &user.Email, &user.Name, &user.AvatarURL, &user.IsAdmin, &user.CreatedAt)
+	if err != nil {
+		respondError(c, http.StatusConflict, "CONFLICT", "user already exists")
+		return
+	}
+
+	userUUID, _ := uuid.Parse(user.ID)
+	if err := q.MarkUserInviteUsed(c.Request.Context(), sqlcdb.MarkUserInviteUsedParams{
+		ID:     invite.ID,
+		UsedBy: uuid.NullUUID{UUID: userUUID, Valid: userUUID != uuid.Nil},
+	}); err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to consume invite")
+		return
+	}
+
+	jwtSecret := c.MustGet("jwt_secret").(string)
+	token, err := generateJWT(user.ID, user.Email, jwtSecret)
+	if err != nil {
+		respondError(c, http.StatusInternalServerError, "INTERNAL", "failed to generate token")
+		return
+	}
+	c.JSON(http.StatusCreated, AuthResponse{Token: token, User: user})
+}