refactor: BaseModel 主键列名统一 uid→id

- BaseModel 移除 gorm column:uid 和 json:uid 标签，统一为 id
- 更新 8 个 repository 文件中 28 处 raw SQL 列引用 (uid→id)
- 更新 3 个前端 JS 文件中 14 处 API 响应字段引用 (uid→id)
- 添加数据库迁移 SQL 脚本 (docs/migrations/001_uid_to_id.sql)

internal/repository/follow_repo.go

@@ -72,7 +72,7 @@ func (r *FollowRepo) ListFollowers(userID uint, offset, limit int) ([]model.User
 	var items []model.UserFollow
 	err := r.db.Table("user_follows").
 		Select("user_follows.*, u.username AS follower_username, u.avatar AS follower_avatar, u.bio AS follower_bio").
-		Joins("INNER JOIN users u ON u.uid = user_follows.follower_id").
+		Joins("INNER JOIN users u ON u.id = user_follows.follower_id").
 		Where("user_follows.followee_id = ?", userID).
 		Order("user_follows.created_at DESC").
 		Offset(offset).Limit(limit).
@@ -89,7 +89,7 @@ func (r *FollowRepo) ListFollowing(userID uint, offset, limit int) ([]model.User
 	var items []model.UserFollow
 	err := r.db.Table("user_follows").
 		Select("user_follows.*, u.username AS followee_username, u.avatar AS followee_avatar, u.bio AS followee_bio").
-		Joins("INNER JOIN users u ON u.uid = user_follows.followee_id").
+		Joins("INNER JOIN users u ON u.id = user_follows.followee_id").
 		Where("user_follows.follower_id = ?", userID).
 		Order("user_follows.created_at DESC").
 		Offset(offset).Limit(limit).
@@ -100,14 +100,14 @@ func (r *FollowRepo) ListFollowing(userID uint, offset, limit int) ([]model.User
 // IncrFollowersCount 原子增减粉丝数
 func (r *FollowRepo) IncrFollowersCount(userID uint, delta int) error {
 	return r.db.Model(&model.User{}).
-		Where("uid = ?", userID).
+		Where("id = ?", userID).
 		UpdateColumn("followers_count", gorm.Expr("followers_count + ?", delta)).Error
 }
 
 // IncrFollowingCount 原子增减关注数
 func (r *FollowRepo) IncrFollowingCount(userID uint, delta int) error {
 	return r.db.Model(&model.User{}).
-		Where("uid = ?", userID).
+		Where("id = ?", userID).
 		UpdateColumn("following_count", gorm.Expr("following_count + ?", delta)).Error
 }
 
@@ -116,7 +116,7 @@ func (r *FollowRepo) GetFollowListPublic(userID uint) (bool, error) {
 	var listPublic bool
 	err := r.db.Model(&model.User{}).
 		Select("follow_list_public").
-		Where("uid = ?", userID).
+		Where("id = ?", userID).
 		Scan(&listPublic).Error
 	return listPublic, err
 }