HH-446: restore auditable quality gates from current main (#102)

* HH-446: restore auditable quality gates

* test(HH-446): restore help center smoke contract

---------

Co-authored-by: Rogee <rogee@ipao.vip>

backend/scripts/validate_health_json.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""Validate the stable JSON contract returned by GET /health."""
+
+import argparse
+import json
+import sys
+from datetime import datetime
+from pathlib import Path
+
+
+def validate(value):
+    if not isinstance(value, dict):
+        return "health response must be a JSON object"
+    missing = sorted({"status", "timestamp", "uptime", "checks"} - value.keys())
+    if missing:
+        return f"health response missing fields: {', '.join(missing)}"
+    if value["status"] != "healthy":
+        return f"unexpected health status: {value['status']}"
+    try:
+        datetime.fromisoformat(value["timestamp"].replace("Z", "+00:00"))
+    except (AttributeError, ValueError):
+        return "timestamp must be RFC3339"
+    if not isinstance(value["uptime"], str) or not value["uptime"]:
+        return "uptime must be a non-empty string"
+    if not isinstance(value["checks"], dict) or value["checks"].get("database") != "healthy":
+        return "database health check must be healthy"
+    return None
+
+
+def main(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument("path", nargs="?", help="JSON file; stdin when omitted")
+    args = parser.parse_args(argv)
+    try:
+        raw = Path(args.path).read_text(encoding="utf-8") if args.path else sys.stdin.read()
+        error = validate(json.loads(raw))
+    except (OSError, json.JSONDecodeError) as exc:
+        error = f"invalid health JSON: {exc}"
+    if error:
+        print(error, file=sys.stderr)
+        return 1
+    print("health JSON contract: ok")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())