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/app/api/knowledge.py

@@ -18,6 +18,7 @@ from app.auth_middleware import require_role
 from app.deps import get_entity_id
 from app.models import KnowledgeEvent, KnowledgeSummary
 from app.services.knowledge_service import (
+    DeepSeekKeyMissing,
     generate_summary_sync,
     generate_daily_sync,
     generate_weekly_sync,
@@ -150,6 +151,9 @@ def trigger_daily_summary(
     try:
         result = generate_daily_sync(db, entity_id=entity_id)
         return {"message": "每日摘要已生成", "summary": result}
+    except DeepSeekKeyMissing as e:
+        logger.error("每日摘要生成失败（缺少 DeepSeek Key）: %s", e)
+        raise HTTPException(status_code=503, detail=str(e))
     except Exception as e:
         logger.exception("每日摘要生成失败")
         raise HTTPException(status_code=500, detail=f"生成失败: {str(e)}")
@@ -164,6 +168,9 @@ def trigger_weekly_summary(
     try:
         result = generate_weekly_sync(db, entity_id=entity_id)
         return {"message": "周度摘要已生成", "summary": result}
+    except DeepSeekKeyMissing as e:
+        logger.error("周度摘要生成失败（缺少 DeepSeek Key）: %s", e)
+        raise HTTPException(status_code=503, detail=str(e))
     except Exception as e:
         logger.exception("周度摘要生成失败")
         raise HTTPException(status_code=500, detail=f"生成失败: {str(e)}")
@@ -178,6 +185,9 @@ def trigger_monthly_summary(
     try:
         result = generate_monthly_sync(db, entity_id=entity_id)
         return {"message": "月度摘要已生成", "summary": result}
+    except DeepSeekKeyMissing as e:
+        logger.error("月度摘要生成失败（缺少 DeepSeek Key）: %s", e)
+        raise HTTPException(status_code=503, detail=str(e))
     except Exception as e:
         logger.exception("月度摘要生成失败")
         raise HTTPException(status_code=500, detail=f"生成失败: {str(e)}")

backend/app/services/knowledge_service.py

@@ -39,9 +39,23 @@ KPI变化：列出核心指标变化（名称、方向、幅度）
 注意：如果事件列表为空或没有有价值的信息，直接输出"本期无重要变化"。"""
 
 
+class DeepSeekKeyMissing(RuntimeError):
+    """DEEPSEEK_API_KEY 未配置 —— 禁止用硬编码默认 Key 兜底（2026-10-18 代码卫生）。"""
+
+
+def _require_deepseek_key() -> str:
+    """强制从环境变量读取 DeepSeek Key；缺失即抛明确错误，绝不静默使用假 Key。"""
+    api_key = (os.getenv("DEEPSEEK_API_KEY") or "").strip()
+    if not api_key:
+        raise DeepSeekKeyMissing(
+            "DEEPSEEK_API_KEY 未配置（knowledge_service 禁止硬编码默认 key）"
+        )
+    return api_key
+
+
 async def _call_deepseek(prompt: str, timeout: int = 30) -> str:
     """调用DeepSeek API生成摘要"""
-    api_key = os.getenv("DEEPSEEK_API_KEY", "sk-8e2...c2e8")
+    api_key = _require_deepseek_key()  # 缺 env 直接抛，不拿假 Key 发请求
     try:
         async with httpx.AsyncClient(timeout=timeout) as client:
             resp = await client.post(