feat(canvas): 画布资源 - 缩略图字段与缓存加载支持

backend/internal/database/migrations.go

@@ -11,7 +11,7 @@ import (
 	"gorm.io/gorm"
 )
 
-const CurrentSchemaVersion int64 = 40
+const CurrentSchemaVersion int64 = 41
 
 const baselineSchemaChecksum = "sha256:open-ai-canvas-schema-v1-20260830"
 const schemaMigrationAppliedAtIndexChecksum = "sha256:schema-migrations-applied-at-index-v2-20260830"
@@ -28,6 +28,7 @@ const cloudAgentGeminiCacheIdentityChecksum = "sha256:cloud-agent-gemini-cache-i
 const prefixedIDSequenceReconcileChecksum = "sha256:prefixed-id-sequence-reconcile-v38-20260926"
 const skillLibraryCategoriesChecksum = "sha256:skill-library-categories-v39-20260926"
 const builtinSkillTombstonesChecksum = "sha256:builtin-skill-tombstones-v40-20260927"
+const resourceThumbnailChecksum = "sha256:resource-thumbnail-v41-20260927"
 
 const postgresSchemaMigrationLockID int64 = 73123910420260830
 
@@ -135,6 +136,9 @@ var schemaMigrations = []migration{
 	{version: 40, name: "builtin_skill_tombstones", checksum: builtinSkillTombstonesChecksum, apply: func(tx *gorm.DB) error {
 		return tx.AutoMigrate(&model.BuiltinSkillTombstone{})
 	}},
+	{version: 41, name: "resource_thumbnail", checksum: resourceThumbnailChecksum, apply: func(tx *gorm.DB) error {
+		return tx.AutoMigrate(&model.Resource{})
+	}},
 }
 
 func migratePrefixedIDSequenceReconcile(tx *gorm.DB) error {

backend/internal/model/models_project.go

@@ -51,6 +51,12 @@ type Resource struct {
 	PlaybackStatus    string `json:"playbackStatus" gorm:"index;size:24"`
 	PlaybackObjectKey string `json:"playbackObjectKey"`
 	PlaybackError     string `json:"playbackError" gorm:"type:text"`
+	// 单档画布展示缩略图；对象键固定由 ObjectKey 派生，不单独持久化。
+	ThumbnailStatus   string `json:"thumbnailStatus" gorm:"size:24"`
+	ThumbnailMimeType string `json:"thumbnailMimeType" gorm:"size:120"`
+	ThumbnailSize     int64  `json:"thumbnailSize"`
+	ThumbnailWidth    int    `json:"thumbnailWidth"`
+	ThumbnailHeight   int    `json:"thumbnailHeight"`
 	// UploadKey 是客户端逻辑上传身份的摘要；NULL 表示不参与幂等约束。
 	UploadKey *string   `json:"-" gorm:"size:64;uniqueIndex:idx_resources_user_upload_key,priority:2"`
 	Error     string    `json:"error"`

backend/internal/repository/repository.go

@@ -1008,6 +1008,14 @@ func (r *Repository) SaveResource(resource *model.Resource) error {
 	return r.db.Save(resource).Error
 }
 
+// UpdateResourceThumbnail only updates a still-ready row and cannot resurrect a deleted resource.
+func (r *Repository) UpdateResourceThumbnail(userID string, id string, values map[string]any) (bool, error) {
+	result := r.db.Model(&model.Resource{}).
+		Where("id = ? AND user_id = ? AND status = ?", id, userID, model.ResourceStatusReady).
+		Updates(values)
+	return result.RowsAffected == 1, result.Error
+}
+
 func (r *Repository) ResourceByUploadKey(userID string, uploadKey string) (*model.Resource, error) {
 	var resource model.Resource
 	if err := r.db.First(&resource, "user_id = ? AND upload_key = ?", userID, uploadKey).Error; err != nil {