feat: add recent canvas backups endpoint

- Introduced a new endpoint to retrieve the most recent canvas backups for authenticated users.
- Implemented logic to limit the number of backups returned based on a maximum configured value.
- Enhanced the canvas router with JWT decoding to identify the user associated with the backups.

Author: atyrode

src/backend/routers/canvas.py

@@ -1,11 +1,11 @@
 import json
 import jwt
-from typing import Dict, Any
+from typing import Dict, Any, List
 from fastapi import APIRouter, HTTPException, Depends, Request
 from fastapi.responses import JSONResponse
 
 from dependencies import SessionData, require_auth
-from db import store_canvas_data, get_canvas_data
+from db import store_canvas_data, get_canvas_data, get_recent_canvases, MAX_BACKUPS_PER_USER
 import posthog
 
 canvas_router = APIRouter()
@@ -74,3 +74,17 @@ async def get_canvas(auth: SessionData = Depends(require_auth)):
     if data is None:
         return get_default_canvas_data()
     return data
+
+@canvas_router.get("/recent")
+async def get_recent_canvas_backups(limit: int = MAX_BACKUPS_PER_USER, auth: SessionData = Depends(require_auth)):
+    """Get the most recent canvas backups for the authenticated user"""
+    access_token = auth.token_data.get("access_token")
+    decoded = jwt.decode(access_token, options={"verify_signature": False})
+    user_id = decoded["sub"]
+    
+    # Limit the number of backups to the maximum configured value
+    if limit > MAX_BACKUPS_PER_USER:
+        limit = MAX_BACKUPS_PER_USER
+    
+    backups = await get_recent_canvases(user_id, limit)
+    return {"backups": backups}