feat: 并发分组系统 + 品牌/Logo 上传 + 兑换码开关 + 文档分辨率表

并发分组(新功能):
- 新表 concurrency_groups(名称/上限/默认),用户加 concurrency_group_id
- 启动自动建「默认并发」组(上限10、默认),老用户回填、新注册自动绑定
- 并发计数改用 Redis(自愈 sorted-set + TTL + fail-open):
  · 用户并发(画图台 + API key 合计)受其分组上限限制,0=不限制 → 超返回 429
  · 账号级并发也从内存 gate 换成同一套 Redis(6 处调用点)
  · 移除旧的「已有正在生成的任务」单任务锁
- 后台「并发分组」新菜单:增删改、设默认、用户数;默认组不可删(删别的组成员转默认)
- 用户管理:并发列 + 新建/编辑可选分组
- 个人设置页:账户信息卡(用户名/邮箱/角色/余额/并发);/me 暴露 concurrency_group/limit

品牌 / Logo(上传到 RustFS):
- Logo 改成拖拽/点击上传,点保存才上传;替换自动删旧;branding/ 设为公开且被清理任务 pin 住(永不删)
- 有自定义就用:前台左侧 nav + 后台侧栏 + favicon(浏览器标签);没有则默认 V 图标
- 前台页头还原成文字;首页 Hero 子标题用 site.subtitle(默认那句宣传语,设置页预填)
- 邮件验证码标题用站点名;新增 POST/DELETE /settings/logo + POST /settings/asset(首页底图上传)

兑换码开关:
- 系统设置→积分 新增「开启兑换码」(默认开);关闭后后端拒绝兑换、前台隐藏兑换入口(/site 暴露 cdk_redeem_enabled)

文档 / 分辨率:
- 去掉 quality 参数:size(宽x高)同时决定比例 + 分辨率档(长边映射 1K/2K/4K)
- 文档加「分辨率对照表」(14 个比例 × 1K/2K/4K → size 该传的值);guessRatio 与自定义模型 RATIO_OPTS 对齐到 14 个

其它:
- 删模型时同步清掉各上游账号「支持模型」里的该 id
- 首页设置/兑换码弹窗去固定高度滚动条;展示位弹窗浅色主题适配

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/internal/service/app_settings.go

@@ -41,10 +41,11 @@ type SMTPSettings struct {
 }
 
 type CreditSettings struct {
-	CheckinEnabled bool `json:"checkin_enabled"`
-	CheckinReward  int  `json:"checkin_reward"`
-	InviteEnabled  bool `json:"invite_enabled"`
-	InviteReward   int  `json:"invite_reward"`
+	CheckinEnabled   bool `json:"checkin_enabled"`
+	CheckinReward    int  `json:"checkin_reward"`
+	InviteEnabled    bool `json:"invite_enabled"`
+	InviteReward     int  `json:"invite_reward"`
+	CDKRedeemEnabled bool `json:"cdk_redeem_enabled"`
 }
 
 type ProxySettings struct {
@@ -70,6 +71,75 @@ func NewAppSettingsService(settings *repo.SiteSettingRepository, events *repo.Ev
 	}
 }
 
+// UploadLogo stores a new site logo in object storage under branding/, deletes
+// the previously-uploaded one (if any), persists site.logo, and returns its URL.
+func (s *AppSettingsService) UploadLogo(ctx context.Context, data []byte, contentType string) (string, error) {
+	if s.store == nil || !s.store.Configured() {
+		return "", errors.New("对象存储未配置")
+	}
+	if len(data) == 0 {
+		return "", errors.New("空文件")
+	}
+	if len(data) > 4*1024*1024 {
+		return "", errors.New("logo 不能超过 4MB")
+	}
+	key := "branding/logo-" + randomUpper(10) + "." + logoExt(contentType)
+	if err := s.store.Put(ctx, key, data, contentType); err != nil {
+		return "", err
+	}
+	url := "/images/" + key
+	// Delete the previous uploaded logo (best-effort), then point site.logo at the new one.
+	if old, _ := s.settings.GetValue(ctx, "site.logo"); strings.HasPrefix(old, "/images/branding/") {
+		_ = s.store.Delete(ctx, strings.TrimPrefix(old, "/images/"))
+	}
+	if err := s.settings.UpsertValue(ctx, "site.logo", url); err != nil {
+		return "", err
+	}
+	return url, nil
+}
+
+// UploadAsset stores a public image (e.g. a 首页内容 底图) under branding/ and
+// returns its storage path (for form.image). Does NOT touch site settings.
+func (s *AppSettingsService) UploadAsset(ctx context.Context, data []byte, contentType string) (string, error) {
+	if s.store == nil || !s.store.Configured() {
+		return "", errors.New("对象存储未配置")
+	}
+	if len(data) == 0 {
+		return "", errors.New("空文件")
+	}
+	if len(data) > 8*1024*1024 {
+		return "", errors.New("图片不能超过 8MB")
+	}
+	key := "branding/sc-" + randomUpper(10) + "." + logoExt(contentType)
+	if err := s.store.Put(ctx, key, data, contentType); err != nil {
+		return "", err
+	}
+	return key, nil
+}
+
+// RemoveLogo deletes the uploaded logo and resets site.logo to the built-in default (empty).
+func (s *AppSettingsService) RemoveLogo(ctx context.Context) error {
+	if old, _ := s.settings.GetValue(ctx, "site.logo"); strings.HasPrefix(old, "/images/branding/") && s.store != nil {
+		_ = s.store.Delete(ctx, strings.TrimPrefix(old, "/images/"))
+	}
+	return s.settings.UpsertValue(ctx, "site.logo", "")
+}
+
+func logoExt(contentType string) string {
+	switch strings.ToLower(strings.TrimSpace(contentType)) {
+	case "image/jpeg", "image/jpg":
+		return "jpg"
+	case "image/webp":
+		return "webp"
+	case "image/svg+xml":
+		return "svg"
+	case "image/gif":
+		return "gif"
+	default:
+		return "png"
+	}
+}
+
 func (s *AppSettingsService) Registration(ctx context.Context) (*RegistrationSettings, error) {
 	openRaw, err := s.settings.GetValue(ctx, "auth.open")
 	if err != nil {
@@ -281,11 +351,13 @@ func (s *AppSettingsService) Credits(ctx context.Context) (*CreditSettings, erro
 	if err != nil {
 		return nil, err
 	}
+	cdkRaw, _ := s.settings.GetValue(ctx, "credits.cdk_redeem_enabled")
 	return &CreditSettings{
-		CheckinEnabled: parseBoolSetting(checkinEnabledRaw, true),
-		CheckinReward:  parseIntSetting(checkinRewardRaw, 3),
-		InviteEnabled:  parseBoolSetting(inviteEnabledRaw, true),
-		InviteReward:   parseIntSetting(inviteRewardRaw, 3),
+		CheckinEnabled:   parseBoolSetting(checkinEnabledRaw, true),
+		CheckinReward:    parseIntSetting(checkinRewardRaw, 3),
+		InviteEnabled:    parseBoolSetting(inviteEnabledRaw, true),
+		InviteReward:     parseIntSetting(inviteRewardRaw, 3),
+		CDKRedeemEnabled: parseBoolSetting(cdkRaw, true),
 	}, nil
 }
 
@@ -297,10 +369,11 @@ func (s *AppSettingsService) SaveCredits(ctx context.Context, in CreditSettings)
 		in.InviteReward = 0
 	}
 	if err := s.settings.UpsertValues(ctx, map[string]string{
-		"credits.checkin_enabled": strconv.FormatBool(in.CheckinEnabled),
-		"credits.checkin_reward":  strconv.Itoa(in.CheckinReward),
-		"credits.invite_enabled":  strconv.FormatBool(in.InviteEnabled),
-		"credits.invite_reward":   strconv.Itoa(in.InviteReward),
+		"credits.checkin_enabled":   strconv.FormatBool(in.CheckinEnabled),
+		"credits.checkin_reward":    strconv.Itoa(in.CheckinReward),
+		"credits.invite_enabled":    strconv.FormatBool(in.InviteEnabled),
+		"credits.invite_reward":     strconv.Itoa(in.InviteReward),
+		"credits.cdk_redeem_enabled": strconv.FormatBool(in.CDKRedeemEnabled),
 	}); err != nil {
 		return nil, err
 	}