refactor(repository): 收敛 model/repository 分层为唯一持久化入口

将 OpenFlare 与平台业务的数据访问从 model 与 apps 直连迁入 repository，
model 仅保留实体与无 IO 规则；补充 code-check 架构守卫与开发规范。

internal/repository/user.go

@@ -5,8 +5,11 @@ package repository
 
 import (
 	"context"
+	"errors"
+	"time"
 
 	db "github.com/Rain-kl/Wavelet/internal/infra/persistence"
+	"github.com/Rain-kl/Wavelet/internal/infra/persistence/idgen"
 	"github.com/Rain-kl/Wavelet/internal/model"
 	"gorm.io/gorm"
 )
@@ -175,7 +178,117 @@ func ListUsersByIDs(ctx context.Context, ids []uint64) ([]model.User, error) {
 	return users, nil
 }
 
+// ListUserIDsByUsernameContains returns user IDs whose username contains the given fragment.
+func ListUserIDsByUsernameContains(ctx context.Context, username string) ([]uint64, error) {
+	if username == "" {
+		return []uint64{}, nil
+	}
+	var userIDs []uint64
+	if err := db.DB(ctx).Model(&model.User{}).
+		Where("username LIKE ?", "%"+username+"%").
+		Pluck("id", &userIDs).Error; err != nil {
+		return nil, err
+	}
+	return userIDs, nil
+}
+
 // UpdateUser updates all fields of an existing user.
 func UpdateUser(ctx context.Context, user *model.User) error {
 	return db.DB(ctx).Save(user).Error
 }
+
+// CreateUserFromOAuth creates a user from OAuth profile data and fills userOut.
+func CreateUserFromOAuth(ctx context.Context, userOut *model.User, oauthInfo *model.OAuthUserInfo) error {
+	now := time.Now()
+	userID := oauthInfo.GetID()
+	newUser := model.User{
+		ID:          userID,
+		Username:    oauthInfo.Username,
+		Nickname:    oauthInfo.Name,
+		Email:       oauthInfo.Email,
+		AvatarURL:   oauthInfo.AvatarURL,
+		IsActive:    oauthInfo.Active,
+		LastLoginAt: now,
+		IsAdmin:     false,
+	}
+	if newUser.ID == 0 {
+		newUser.ID = idgen.NextUint64ID()
+	}
+	if err := db.DB(ctx).Create(&newUser).Error; err != nil {
+		return err
+	}
+	*userOut = newUser
+	return nil
+}
+
+// ListUsernamesMatchingBase returns usernames equal to base or prefixed with base+"-".
+func ListUsernamesMatchingBase(ctx context.Context, base string) ([]string, error) {
+	var names []string
+	if err := db.DB(ctx).Model(&model.User{}).
+		Where("username = ? OR username LIKE ?", base, base+"-%").
+		Pluck("username", &names).Error; err != nil {
+		return nil, err
+	}
+	return names, nil
+}
+
+// GetActiveUserByID loads a user by ID who is active.
+func GetActiveUserByID(ctx context.Context, id uint64) (model.User, error) {
+	var user model.User
+	if err := db.DB(ctx).Where("id = ? AND is_active = ?", id, true).First(&user).Error; err != nil {
+		return model.User{}, err
+	}
+	return user, nil
+}
+
+// GetUserByUsernameOrEmail loads a user by username or email.
+func GetUserByUsernameOrEmail(ctx context.Context, input string) (model.User, error) {
+	var user model.User
+	if err := db.DB(ctx).Where("username = ? OR email = ?", input, input).First(&user).Error; err != nil {
+		return model.User{}, err
+	}
+	return user, nil
+}
+
+// CountUsersByEmailExceptID counts users with the email excluding a given user id.
+func CountUsersByEmailExceptID(ctx context.Context, email string, exceptID uint64) (int64, error) {
+	var count int64
+	if err := db.DB(ctx).Model(&model.User{}).Where("email = ? AND id != ?", email, exceptID).Count(&count).Error; err != nil {
+		return 0, err
+	}
+	return count, nil
+}
+
+// UpdateUserLastLoginAt updates only last_login_at for a user.
+func UpdateUserLastLoginAt(ctx context.Context, userID uint64, at time.Time) error {
+	return db.DB(ctx).Model(&model.User{}).Where("id = ?", userID).Update("last_login_at", at).Error
+}
+
+// UpdateUserPassword updates only the password hash for a user.
+func UpdateUserPassword(ctx context.Context, userID uint64, passwordHash string) error {
+	return db.DB(ctx).Model(&model.User{}).Where("id = ?", userID).Update("password", passwordHash).Error
+}
+
+// RegisterUserWithChecks validates username/email uniqueness then creates the user.
+func RegisterUserWithChecks(ctx context.Context, user *model.User) error {
+	var count int64
+	if err := db.DB(ctx).Model(&model.User{}).Where("username = ?", user.Username).Count(&count).Error; err != nil {
+		return err
+	}
+	if count > 0 {
+		return errors.New("用户名已存在")
+	}
+	if user.Email != "" {
+		var emailCount int64
+		if err := db.DB(ctx).Model(&model.User{}).Where("email = ?", user.Email).Count(&emailCount).Error; err != nil {
+			return err
+		}
+		if emailCount > 0 {
+			return errors.New("该邮箱已被其他账号绑定")
+		}
+	}
+	if user.ID == 0 {
+		user.ID = idgen.NextUint64ID()
+	}
+	return db.DB(ctx).Create(user).Error
+}