chore: baseline snapshot before moderation-strictness feature

Repo .git was damaged (refs/ missing, index truncated, object store near-empty).
Repaired via git init (rebuilt refs), stale index preserved as .git/index.corrupt-20260910.bak,
then full worktree committed as a rollback baseline.

internal/db/message_image.go

@@ -0,0 +1,63 @@
+package db
+
+import (
+	"context"
+
+	"github.com/pkg/errors"
+	"gorm.io/gorm"
+)
+
+var MessageImages MessageImageStore
+
+type MessageImageStore interface {
+	Create(ctx context.Context, opts CreateMessageImageOptions) (*MessageImage, error)
+	GetByMessageIDs(ctx context.Context, messageIDs []uint) (map[uint][]*MessageImage, error)
+}
+
+func NewMessageImageStore(db *gorm.DB) MessageImageStore {
+	return &messageImages{db}
+}
+
+type messageImages struct {
+	*gorm.DB
+}
+
+type MessageImage struct {
+	gorm.Model
+	MessageID uint   `gorm:"index" json:"message_id"`
+	URL       string `gorm:"size:500" json:"url"`
+	FileName  string `gorm:"size:200" json:"file_name"`
+	FileSize  int64  `json:"file_size"`
+}
+
+type CreateMessageImageOptions struct {
+	MessageID uint
+	URL       string
+	FileName  string
+	FileSize  int64
+}
+
+func (db *messageImages) Create(ctx context.Context, opts CreateMessageImageOptions) (*MessageImage, error) {
+	img := &MessageImage{
+		MessageID: opts.MessageID,
+		URL:       opts.URL,
+		FileName:  opts.FileName,
+		FileSize:  opts.FileSize,
+	}
+	if err := db.WithContext(ctx).Create(img).Error; err != nil {
+		return nil, errors.Wrap(err, "create message image")
+	}
+	return img, nil
+}
+
+func (db *messageImages) GetByMessageIDs(ctx context.Context, messageIDs []uint) (map[uint][]*MessageImage, error) {
+	var images []*MessageImage
+	if err := db.WithContext(ctx).Where("message_id IN ?", messageIDs).Find(&images).Error; err != nil {
+		return nil, errors.Wrap(err, "get message images")
+	}
+	result := make(map[uint][]*MessageImage)
+	for _, img := range images {
+		result[img.MessageID] = append(result[img.MessageID], img)
+	}
+	return result, nil
+}