fix(invites): register strftime Jinja2 filter, fix 500 error on admin invites page

app/routers/web.py

@@ -50,6 +50,14 @@ def _to_local(dt: datetime) -> datetime:
 templates.env.filters["to_local"] = _to_local
 
 
+def _strftime(dt: datetime, fmt: str) -> str:
+    """Format a datetime with strftime."""
+    return dt.strftime(fmt) if dt else ""
+
+
+templates.env.filters["strftime"] = _strftime
+
+
 def _redirect(url: str) -> RedirectResponse:
     return RedirectResponse(url, status_code=303)