fix(postcard): mark-delivered stays on current page via fetch+reload instead of redirect

app/routers/web.py

@@ -898,7 +898,7 @@ def postcard_delete(postcard_id: int, user: User = Depends(get_current_user_web)
 
 
 @router.post("/postcards/{postcard_id}/mark-delivered")
-def mark_delivered(
+async def mark_delivered(
     postcard_id: int,
     user: User = Depends(get_current_user_web),
     db: Session = Depends(get_db),
@@ -910,12 +910,12 @@ def mark_delivered(
         .first()
     )
     if not pc:
-        return _redirect("/profiles")
+        return JSONResponse({"ok": False}, status_code=404)
     pc.status = "delivered"
     if not pc.arrival_time:
         pc.arrival_time = datetime.now()
     db.commit()
-    return _redirect(f"/postcards/{postcard_id}")
+    return JSONResponse({"ok": True})
 
 
 @router.post("/postcards/{postcard_id}/mark-sent")