feat: enhance Letzshop jobs and order management

- Add job cancellation and retry functionality
- Improve jobs table with better status display
- Add background task improvements
- Update Letzshop order service
- Update documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/schema/letzshop.py

@@ -436,11 +436,18 @@ class LetzshopJobItem(BaseModel):
     records_processed: int = 0
     records_succeeded: int = 0
     records_failed: int = 0
+    # Vendor info
+    vendor_id: int | None = Field(None, description="Vendor ID")
+    vendor_name: str | None = Field(None, description="Vendor name")
+    vendor_code: str | None = Field(None, description="Vendor code")
     # Historical import specific fields
     current_phase: str | None = Field(
         None, description="Current phase for historical imports"
     )
     error_message: str | None = Field(None, description="Error message if failed")
+    error_details: dict[str, Any] | None = Field(
+        None, description="Error details or export file info"
+    )
 
 
 class LetzshopJobsListResponse(BaseModel):