Feat: support agent version history. (#6130)

### What problem does this PR solve?
Add history version save
- Allows users to view and download agent files by version revision
history

![image](https://github.com/user-attachments/assets/c300375d-8b97-4230-9fc4-83d148137132)

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

api/db/db_models.py

@@ -988,6 +988,16 @@ class CanvasTemplate(DataBaseModel):
     class Meta:
         db_table = "canvas_template"
 
+class UserCanvasVersion(DataBaseModel):
+    id = CharField(max_length=32, primary_key=True)
+    user_canvas_id = CharField(max_length=255, null=False, help_text="user_canvas_id", index=True)
+
+    title = CharField(max_length=255, null=True, help_text="Canvas title")
+    description = TextField(null=True, help_text="Canvas description")
+    dsl = JSONField(null=True, default={})
+
+    class Meta:
+        db_table = "user_canvas_version"
 
 def migrate_db():
     with DB.transaction():