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/admin_write.go

@@ -27,15 +27,17 @@ type AdminWriteService struct {
 	models   *repo.ModelRepository
 	events   *repo.EventRepository
 	apiKeys  *repo.APIKeyRepository
+	tokens   *repo.TokenRepository
 }
 
-func NewAdminWriteService(users *repo.UserRepository, showcase *repo.ShowcaseRepository, models *repo.ModelRepository, events *repo.EventRepository, apiKeys *repo.APIKeyRepository) *AdminWriteService {
+func NewAdminWriteService(users *repo.UserRepository, showcase *repo.ShowcaseRepository, models *repo.ModelRepository, events *repo.EventRepository, apiKeys *repo.APIKeyRepository, tokens *repo.TokenRepository) *AdminWriteService {
 	return &AdminWriteService{
 		users:    users,
 		showcase: showcase,
 		models:   models,
 		events:   events,
 		apiKeys:  apiKeys,
+		tokens:   tokens,
 	}
 }
 
@@ -60,6 +62,7 @@ func (s *AdminWriteService) CreateUser(ctx context.Context, body map[string]any)
 	status := normalizedStatus(stringValue(body["status"]))
 	credits := maxFloat(0, floatValue(body["credits"]))
 	notes := strings.TrimSpace(stringValue(body["notes"]))
+	cgroupID := strings.TrimSpace(stringValue(body["concurrency_group_id"]))
 
 	exists, err := s.users.ExistsEmail(ctx, email, "")
 	if err != nil {
@@ -99,6 +102,7 @@ func (s *AdminWriteService) CreateUser(ctx context.Context, body map[string]any)
 		Status:       status,
 		Credits:      credits,
 		Notes:        notes,
+		ConcurrencyGroupID: cgroupID,
 		InviteCode:   randomInviteCode(),
 		CreatedAt:    time.Now(),
 		UpdatedAt:    time.Now(),
@@ -161,6 +165,9 @@ func (s *AdminWriteService) UpdateUser(ctx context.Context, userID string, body
 	if _, ok := body["notes"]; ok {
 		patch["notes"] = strings.TrimSpace(stringValue(body["notes"]))
 	}
+	if _, ok := body["concurrency_group_id"]; ok {
+		patch["concurrency_group_id"] = strings.TrimSpace(stringValue(body["concurrency_group_id"]))
+	}
 	if _, ok := body["password"]; ok && strings.TrimSpace(stringValue(body["password"])) != "" {
 		if err := ValidatePassword(stringValue(body["password"])); err != nil {
 			return nil, err
@@ -458,9 +465,52 @@ func (s *AdminWriteService) DeleteModel(ctx context.Context, modelID string) err
 	if rows == 0 {
 		return ErrNotFound
 	}
+	// Clean up: strip this model id from every custom upstream account's
+	// supported-models list so no orphan reference is left behind.
+	s.removeModelFromUpstreams(ctx, modelID)
 	return nil
 }
 
+// removeModelFromUpstreams drops modelID from the CSV in each custom account's
+// Meta["models"]. Best-effort — a failure here doesn't undo the model delete.
+func (s *AdminWriteService) removeModelFromUpstreams(ctx context.Context, modelID string) {
+	if s.tokens == nil {
+		return
+	}
+	items, err := s.tokens.ListByPool(ctx, "custom")
+	if err != nil {
+		return
+	}
+	for _, it := range items {
+		raw, _ := it.Meta["models"].(string)
+		if strings.TrimSpace(raw) == "" {
+			continue
+		}
+		kept := make([]string, 0, len(strings.Split(raw, ",")))
+		changed := false
+		for _, p := range strings.Split(raw, ",") {
+			p = strings.TrimSpace(p)
+			if p == "" {
+				continue
+			}
+			if p == modelID {
+				changed = true
+				continue
+			}
+			kept = append(kept, p)
+		}
+		if !changed {
+			continue
+		}
+		meta := datatypes.JSONMap{}
+		for k, v := range it.Meta {
+			meta[k] = v
+		}
+		meta["models"] = strings.Join(kept, ",")
+		_, _ = s.tokens.Update(ctx, "custom", it.ID, map[string]any{"meta": meta})
+	}
+}
+
 func (s *AdminWriteService) ClearLogs(ctx context.Context) (int64, error) {
 	return s.events.DeleteAll(ctx)
 }