feat(observe): 加 OBSERVE_* 配置与 observe_configured 门槛

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_observe.py

@@ -0,0 +1,25 @@
+"""接口指标可观测(observe)单测:配置门槛 / 队列 / 中间件 / worker。
+
+沿用仓库约定:TestClient + monkeypatch,绝不打真网络。observe 默认关(conftest 未设
+OBSERVE_*),需要开启的用例用 monkeypatch 改 settings 单例属性。
+"""
+from __future__ import annotations
+
+from app.core.config import settings
+
+
+def test_observe_configured_requires_switch_and_creds(monkeypatch):
+    # 开关开 + endpoint(默认 localhost)+ user + password 齐全 → True
+    monkeypatch.setattr(settings, "OBSERVE_ENABLED", True)
+    monkeypatch.setattr(settings, "OBSERVE_USER", "u")
+    monkeypatch.setattr(settings, "OBSERVE_PASSWORD", "p")
+    assert settings.observe_configured is True
+
+    # 缺密码 → False
+    monkeypatch.setattr(settings, "OBSERVE_PASSWORD", "")
+    assert settings.observe_configured is False
+
+    # 开关关 → False(即便凭证齐全)
+    monkeypatch.setattr(settings, "OBSERVE_PASSWORD", "p")
+    monkeypatch.setattr(settings, "OBSERVE_ENABLED", False)
+    assert settings.observe_configured is False