feat: add ads/sponsor/captcha modules and polish home & chat UI

backend/model/db.go

@@ -61,7 +61,7 @@ func InitDB(dsn string) error {
 		&Announcement{}, &SitePage{}, &SiteSetting{}, &SiteDailyStats{}, &SiteDailyVisitor{}, &Attachment{}, &UserBoard{}, &LoginLog{},
 		&ChatRoom{}, &ChatRoomMember{}, &ChatMessage{},
 		&PointLedger{}, &PostContentUnlock{}, &PostAttachment{}, &PostAttachmentUnlock{},
-		&PostPollVote{}, &PostLotteryEntry{},
+		&PostPollVote{}, &PostLotteryEntry{}, &Ad{},
 	); err != nil {
 		return fmt.Errorf("自动迁移失败: %w", err)
 	}
@@ -78,6 +78,11 @@ func InitDB(dsn string) error {
 		return fmt.Errorf("login_logs 默认值修正失败: %w", err)
 	}
 
+	// 早期 site_settings.value 可能是 varchar(255)；广告/赞助商 JSON 会超长
+	if err := prepareSiteSettingValueText(db); err != nil {
+		return fmt.Errorf("site_settings.value 扩容失败: %w", err)
+	}
+
 	// 新表结构就位后删除遗留的明文列
 	if err := dropLegacyRefreshTokenColumn(db); err != nil {
 		return fmt.Errorf("refresh token 旧列清理失败: %w", err)
@@ -152,6 +157,28 @@ func prepareAnnouncementPinnedColumn(db *gorm.DB) error {
 	return db.Exec(`ALTER TABLE announcements ADD COLUMN pinned boolean NOT NULL DEFAULT false`).Error
 }
 
+// prepareSiteSettingValueText 将 site_settings.value 从 varchar(255) 扩为 text（幂等）
+func prepareSiteSettingValueText(db *gorm.DB) error {
+	var tableCount int64
+	if err := db.Raw(`SELECT count(1) FROM information_schema.tables WHERE table_name = 'site_settings'`).
+		Scan(&tableCount).Error; err != nil {
+		return err
+	}
+	if tableCount == 0 {
+		return nil
+	}
+	var dataType string
+	if err := db.Raw(`SELECT data_type FROM information_schema.columns
+		WHERE table_name = 'site_settings' AND column_name = 'value'`).
+		Scan(&dataType).Error; err != nil {
+		return err
+	}
+	if dataType == "" || dataType == "text" {
+		return nil
+	}
+	return db.Exec(`ALTER TABLE site_settings ALTER COLUMN value TYPE text`).Error
+}
+
 // prepareRefreshTokenSessionColumns 存量 refresh_tokens 加 logged_in_at / last_used_at：
 // 先可空加列，用 created_at 回填后再收紧 NOT NULL。
 func prepareRefreshTokenSessionColumns(db *gorm.DB) error {