fix(insta-lab): 선별 zero-pref 크래시 가드 + judge max_tokens 상향 + 404 테스트

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

insta-lab/app/selection_judge.py

@@ -43,7 +43,7 @@ def judge_candidates(candidates: List[Dict[str, Any]]) -> Dict[int, float]:
     try:
         client = Anthropic(api_key=ANTHROPIC_API_KEY)
         resp = client.messages.create(
-            model=ANTHROPIC_MODEL_HAIKU, max_tokens=512,
+            model=ANTHROPIC_MODEL_HAIKU, max_tokens=1024,
             messages=[{"role": "user", "content": PROMPT.format(items=items)}],
         )
         return parse_judge_response(resp.content[0].text)