fix(e2e): 修正 HMAC Header 名稱 X-Webhook-Signature → X-Signature-256

- API 期望 X-Signature-256，E2E 腳本使用錯誤的 Header 名稱
- 修復後 Daily E2E Health Check 應能通過

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/scripts/e2e_tool_call_verification.py

@@ -221,9 +221,10 @@ class E2EVerification:
             headers = {"Content-Type": "application/json"}
 
             # 如果有 HMAC Secret，計算簽名
+            # 2026-03-29 Claude Code: 修正 Header 名稱為 X-Signature-256 (與 API 一致)
             if HMAC_SECRET:
                 signature = compute_hmac_signature(HMAC_SECRET, payload_bytes)
-                headers["X-Webhook-Signature"] = signature
+                headers["X-Signature-256"] = signature
                 print_info("HMAC", f"已簽名 ({signature[:20]}...)")
             else:
                 print_warn("無 HMAC Secret - 僅限測試環境")