fix: restore stage-based Alpha check classification

backend/app/platform_checks.py

@@ -1,6 +1,12 @@
 """Classify platform evidence without discarding unknown checks or inferring eligibility."""
 
 
+def check_result(check):
+    """Normalize known upstream result casing without rewriting the raw evidence."""
+    value = check.get("result") if isinstance(check, dict) else None
+    return value.upper() if isinstance(value, str) else None
+
+
 def is_submission_limit(check):
     """Recognize only the confirmed account-limit check; unknown names remain Alpha checks."""
     return isinstance(check, dict) and check.get("name") == "REGULAR_SUBMISSION"
@@ -16,8 +22,8 @@ def split_checks(checks):
 def submission_limits(checks):
     """Summarize the observed limit, never the account's current allowance or reset time."""
     _, limits = split_checks(checks)
-    status = "blocked" if any(c.get("result") == "FAIL" for c in limits) else (
-        "not_blocked" if limits and all(c.get("result") == "PASS" for c in limits) else "unknown"
+    status = "blocked" if any(check_result(c) == "FAIL" for c in limits) else (
+        "not_blocked" if limits and all(check_result(c) == "PASS" for c in limits) else "unknown"
     )
     return {"status": status, "checks": limits,
             "meaning": "仅反映缓存观测时的提交限制，不代表当前额度或正式提交资格"}