feat(marketing): user profile update, ad placement management, logo limits

- Add PUT /auth/profile endpoint for nickname and avatar updates
- Add ad_placements table and CRUD admin API for managing ad units
- Add GET /marketing/ad-config public API for mini-program to fetch ad config
- Reduce logo limit from 10 to 3 per user, add 2MB file size validation

Made-with: Cursor

internal/common/auth/service/auth_service.go

@@ -192,6 +192,31 @@ func (s *AuthService) DevLogin(ctx context.Context, miniProgramID uint) (*LoginR
 	}, nil
 }
 
+// UpdateProfile 更新用户昵称和头像。
+func (s *AuthService) UpdateProfile(ctx context.Context, userID uint, nickname, avatarURL string) (*model.User, error) {
+	tx := s.db.WithContext(ctx)
+	var user model.User
+	if err := tx.First(&user, userID).Error; err != nil {
+		return nil, fmt.Errorf("find user: %w", err)
+	}
+
+	updates := map[string]interface{}{}
+	if nickname != "" {
+		updates["nick_name"] = nickname
+		user.NickName = nickname
+	}
+	if avatarURL != "" {
+		updates["avatar_url"] = avatarURL
+		user.AvatarURL = avatarURL
+	}
+	if len(updates) > 0 {
+		if err := tx.Model(&user).Updates(updates).Error; err != nil {
+			return nil, fmt.Errorf("update profile: %w", err)
+		}
+	}
+	return &user, nil
+}
+
 func (s *AuthService) getSmokeMode(ctx context.Context, uid int) (string, error) {
 	var profile smokemodel.SmokeUserProfile
 	err := s.db.WithContext(ctx).