feat(schedule): add course table screens and navigation

Add complete schedule functionality including:
- Schedule screen with weekly course table view
- Course detail screen with transparent modal presentation
- New ScheduleStack navigator integrated into main tab bar
- Schedule service for API interactions
- Type definitions for course entities

Also includes bug fixes for group invite/request handlers
to include required groupId parameter.

internal/repository/message_repo.go

@@ -2,6 +2,9 @@ package repository
 
 import (
 	"carrot_bbs/internal/model"
+	"context"
+	"fmt"
+	"strings"
 	"time"
 
 	"gorm.io/gorm"
@@ -172,7 +175,7 @@ func (r *MessageRepository) GetParticipant(conversationID string, userID string)
 		if err == gorm.ErrRecordNotFound {
 			// 检查会话是否存在
 			var conv model.Conversation
-			if err := r.db.First(&conv, conversationID).Error; err == nil {
+			if err := r.db.Where("id = ?", conversationID).First(&conv).Error; err == nil {
 				// 会话存在，添加参与者
 				participant = model.ConversationParticipant{
 					ConversationID: conversationID,
@@ -284,7 +287,7 @@ func (r *MessageRepository) UpdateConversationLastSeq(conversationID string, seq
 // GetNextSeq 获取会话的下一个seq值
 func (r *MessageRepository) GetNextSeq(conversationID string) (int64, error) {
 	var conv model.Conversation
-	err := r.db.Select("last_seq").First(&conv, conversationID).Error
+	err := r.db.Select("last_seq").Where("id = ?", conversationID).First(&conv).Error
 	if err != nil {
 		return 0, err
 	}
@@ -296,7 +299,7 @@ func (r *MessageRepository) CreateMessageWithSeq(msg *model.Message) error {
 	return r.db.Transaction(func(tx *gorm.DB) error {
 		// 获取当前seq并+1
 		var conv model.Conversation
-		if err := tx.Select("last_seq").First(&conv, msg.ConversationID).Error; err != nil {
+		if err := tx.Select("last_seq").Where("id = ?", msg.ConversationID).First(&conv).Error; err != nil {
 			return err
 		}
 
@@ -522,3 +525,117 @@ func (r *MessageRepository) HideConversationForUser(conversationID, userID strin
 		Where("conversation_id = ? AND user_id = ?", conversationID, userID).
 		Update("hidden_at", &now).Error
 }
+
+// ParticipantUpdate 参与者更新数据
+type ParticipantUpdate struct {
+	ConversationID string
+	UserID         string
+	LastReadSeq    int64
+}
+
+// BatchWriteMessages 批量写入消息
+// 使用 GORM 的 CreateInBatches 实现高效批量插入
+func (r *MessageRepository) BatchWriteMessages(ctx context.Context, messages []*model.Message) error {
+	if len(messages) == 0 {
+		return nil
+	}
+	return r.db.WithContext(ctx).CreateInBatches(messages, 100).Error
+}
+
+// BatchUpdateParticipants 批量更新参与者（使用 CASE WHEN 优化）
+// 使用单条 SQL 更新多条记录，避免循环执行 UPDATE
+func (r *MessageRepository) BatchUpdateParticipants(ctx context.Context, updates []ParticipantUpdate) error {
+	if len(updates) == 0 {
+		return nil
+	}
+
+	// 构建 CASE WHEN 批量更新 SQL
+	// UPDATE conversation_participants
+	// SET last_read_seq = CASE
+	//   WHEN (conversation_id = '1' AND user_id = 'a') THEN 10
+	//   WHEN (conversation_id = '2' AND user_id = 'b') THEN 20
+	// END,
+	// updated_at = ?
+	// WHERE (conversation_id = '1' AND user_id = 'a')
+	//    OR (conversation_id = '2' AND user_id = 'b')
+
+	var cases []string
+	var whereClauses []string
+	var args []interface{}
+
+	for _, u := range updates {
+		cases = append(cases, "WHEN (conversation_id = ? AND user_id = ?) THEN ?")
+		whereClauses = append(whereClauses, "(conversation_id = ? AND user_id = ?)")
+		args = append(args, u.ConversationID, u.UserID, u.LastReadSeq, u.ConversationID, u.UserID)
+	}
+
+	sql := fmt.Sprintf(`
+		UPDATE conversation_participants
+		SET last_read_seq = CASE %s END,
+			updated_at = ?
+		WHERE %s
+	`, strings.Join(cases, " "), strings.Join(whereClauses, " OR "))
+
+	args = append(args, time.Now())
+
+	return r.db.WithContext(ctx).Exec(sql, args...).Error
+}
+
+// UpdateConversationLastSeqWithContext 更新会话最后消息序号
+func (r *MessageRepository) UpdateConversationLastSeqWithContext(ctx context.Context, convID string, lastSeq int64, lastMsgTime time.Time) error {
+	return r.db.WithContext(ctx).
+		Model(&model.Conversation{}).
+		Where("id = ?", convID).
+		Updates(map[string]interface{}{
+			"last_seq":      lastSeq,
+			"last_msg_time": lastMsgTime,
+			"updated_at":    time.Now(),
+		}).Error
+}
+
+// BatchWriteMessagesWithTx 在事务中批量写入消息
+func (r *MessageRepository) BatchWriteMessagesWithTx(tx *gorm.DB, messages []*model.Message) error {
+	if len(messages) == 0 {
+		return nil
+	}
+	return tx.CreateInBatches(messages, 100).Error
+}
+
+// BatchUpdateParticipantsWithTx 在事务中批量更新参与者
+func (r *MessageRepository) BatchUpdateParticipantsWithTx(tx *gorm.DB, updates []ParticipantUpdate) error {
+	if len(updates) == 0 {
+		return nil
+	}
+
+	var cases []string
+	var whereClauses []string
+	var args []interface{}
+
+	for _, u := range updates {
+		cases = append(cases, "WHEN (conversation_id = ? AND user_id = ?) THEN ?")
+		whereClauses = append(whereClauses, "(conversation_id = ? AND user_id = ?)")
+		args = append(args, u.ConversationID, u.UserID, u.LastReadSeq, u.ConversationID, u.UserID)
+	}
+
+	sql := fmt.Sprintf(`
+		UPDATE conversation_participants
+		SET last_read_seq = CASE %s END,
+			updated_at = ?
+		WHERE %s
+	`, strings.Join(cases, " "), strings.Join(whereClauses, " OR "))
+
+	args = append(args, time.Now())
+
+	return tx.Exec(sql, args...).Error
+}
+
+// UpdateConversationLastSeqWithTx 在事务中更新会话最后消息序号
+func (r *MessageRepository) UpdateConversationLastSeqWithTx(tx *gorm.DB, convID string, lastSeq int64, lastMsgTime time.Time) error {
+	return tx.Model(&model.Conversation{}).
+		Where("id = ?", convID).
+		Updates(map[string]interface{}{
+			"last_seq":      lastSeq,
+			"last_msg_time": lastMsgTime,
+			"updated_at":    time.Now(),
+		}).Error
+}