chore(security): 摘除 knowledge_service 硬编码默认 DeepSeek Key（缺 env 抛明确错误/503）

- knowledge_service: 移除 os.getenv 默认值占位，改 _require_deepseek_key() 必填，缺 env 抛 DeepSeekKeyMissing
- knowledge API: generate/{daily,weekly,monthly} 缺 Key 返回 503（可观测，不再静默走模板兜底）
- finance_bot / verify_zxt_vouchers_json / bot_bridge_push: 凭据改 env 优先（CMA_BOT_KEY_* / CMA_BOT_API_KEYS / CMA_BRIDGE_TOKEN），历史共享键仅作兼容期兜底并告警
- tests: 新增 5 例回归（缺 Key 服务层抛错、API 503；有 Key 正常 200）

(cherry picked from commit 859bd8276d7c5aad4bf10ee3399b6cccc188f064)

backend/scripts/verify_zxt_vouchers_json.py

@@ -47,7 +47,28 @@ def override_get_db():
 app.dependency_overrides[get_db] = override_get_db
 client = TestClient(app)
 
-HDR = {"X-BOT-KEY": "cma-bot-admin-2026"}
+# 凭据来源：CMA_BOT_KEY_ADMIN → CMA_BOT_API_KEYS(role=ceo/admin) → 兼容期历史共享键（P3 待轮换）
+_LEGACY_ADMIN_KEY = "cma-bot-admin-2026"
+
+
+def _resolve_admin_key() -> str:
+    key = (os.getenv("CMA_BOT_KEY_ADMIN") or "").strip()
+    if key:
+        return key
+    raw = (os.getenv("CMA_BOT_API_KEYS") or "").strip()
+    if raw:
+        try:
+            import json as _json
+            for k, v in _json.loads(raw).items():
+                if isinstance(v, dict) and v.get("role") in ("ceo", "admin"):
+                    return k
+        except Exception:
+            pass
+    return _LEGACY_ADMIN_KEY
+
+
+HDR = {"X-BOT-KEY": _resolve_admin_key()}
+
 
 def check(name, cond, detail=""):
     print(("PASS " if cond else "FAIL ") + name + (" | " + detail if detail else ""))