fix: guard verdict check uses 'in' to handle extra characters in DeepSeek response

src/guard.py

@@ -40,7 +40,7 @@ async def is_academic_topic(question: str, client, model: str) -> bool:
             temperature=0,
         )
         verdict = response.choices[0].message.content.strip().upper()
-        return verdict == "IZIN"
+        return "IZIN" in verdict
     except Exception:
         # Jika guard gagal, izinkan saja agar bot tidak mati total
         return True