fix(contracts): decouple DTOs from ORM tags and table name mappings

backend/core/contracts/config.go

@@ -10,18 +10,13 @@ import (
 
 // SystemConfigDTO represents a system configuration key-value entry.
 type SystemConfigDTO struct {
-	Key         string    `json:"key" gorm:"primaryKey;column:key;size:255"`
-	Value       string    `json:"value" gorm:"column:value;type:text"`
-	Type        string    `json:"type" gorm:"column:type;size:50"`
-	Visibility  int       `json:"visibility" gorm:"column:visibility"`
-	Description string    `json:"description" gorm:"column:description;size:500"`
-	UpdatedAt   time.Time `json:"updated_at" gorm:"column:updated_at"`
-	CreatedAt   time.Time `json:"created_at" gorm:"column:created_at"`
-}
-
-// TableName returns the default table name for SystemConfigDTO.
-func (SystemConfigDTO) TableName() string {
-	return "w_system_configs"
+	Key         string    `json:"key"`
+	Value       string    `json:"value"`
+	Type        string    `json:"type"`
+	Visibility  int       `json:"visibility"`
+	Description string    `json:"description"`
+	UpdatedAt   time.Time `json:"updated_at"`
+	CreatedAt   time.Time `json:"created_at"`
 }
 
 // SystemConfigService defines the unified contract for querying and mutating system configurations.

backend/core/contracts/task.go

@@ -71,11 +71,6 @@ type TaskExecutionDTO struct {
 	UpdatedAt    time.Time  `json:"updated_at"`
 }
 
-// TableName returns the default table name for TaskExecutionDTO.
-func (TaskExecutionDTO) TableName() string {
-	return "w_task_executions"
-}
-
 // Canonical triggered_by values persisted on task executions and shown in admin UI.
 const (
 	TaskTriggerSystem   = "system"

backend/core/contracts/upload.go

@@ -23,25 +23,20 @@ type UploadMetadataDTO struct {
 
 // UploadDTO represents an uploaded file record.
 type UploadDTO struct {
-	ID        uint64            `json:"id" gorm:"primaryKey"`
-	UserID    uint64            `json:"user_id" gorm:"index"`
-	FileName  string            `json:"file_name" gorm:"size:255"`
-	FilePath  string            `json:"file_path" gorm:"size:500"`
-	MimeType  string            `json:"mime_type" gorm:"size:100"`
+	ID        uint64            `json:"id"`
+	UserID    uint64            `json:"user_id"`
+	FileName  string            `json:"file_name"`
+	FilePath  string            `json:"file_path"`
+	MimeType  string            `json:"mime_type"`
 	Size      int64             `json:"size"`
-	Hash      string            `json:"hash" gorm:"size:64"`
-	Status    string            `json:"status" gorm:"type:varchar(20)"`
-	Type      string            `json:"type" gorm:"size:50;index"`
-	Metadata  UploadMetadataDTO `json:"metadata" gorm:"serializer:json;type:jsonb"`
+	Hash      string            `json:"hash"`
+	Status    string            `json:"status"`
+	Type      string            `json:"type"`
+	Metadata  UploadMetadataDTO `json:"metadata"`
 	CreatedAt time.Time         `json:"created_at"`
 	UpdatedAt time.Time         `json:"updated_at"`
 }
 
-// TableName returns the default table name for UploadDTO.
-func (UploadDTO) TableName() string {
-	return "w_uploads"
-}
-
 // OpenedUploadDTO encapsulates the retrieved object stream and its metadata.
 type OpenedUploadDTO struct {
 	Upload        UploadDTO