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/tests/test_selection.py

@@ -45,3 +45,11 @@ def test_claude_included_when_provided():
     cands = [_cand(1, "A", "economy", 0.5, NOW)]
     out = score_candidates(cands, [], {"economy": 1.0}, {1: 1.0}, threshold=0.0, now_iso=NOW)
     assert out[0]["breakdown"]["claude"] == 1.0
+
+
+def test_all_zero_prefs_no_crash():
+    cands = [{"id": 1, "keyword": "A", "category": "economy", "score": 0.8,
+              "suggested_at": "2026-06-11T00:00:00Z"}]
+    prefs = {"economy": 0.0, "psychology": 0.0}
+    out = score_candidates(cands, [], prefs, None, threshold=0.0, now_iso="2026-06-11T00:00:00Z")
+    assert out[0]["breakdown"]["account_fit"] == 0.0  # 0가중 → fit 0, 크래시 없음