feat(security): privacy hardening + data export (v0.2.1)

- CORS: default localhost-only origins (was *, allowed any webpage
  to read local health data cross-site); env override MI_FITNESS_CORS_ORIGINS
- Host header allowlist middleware on FastAPI and Flask (DNS-rebinding
  protection); auto-configured for non-loopback binds via CLI
- Move API key passTokens from SQLite plaintext to system keyring,
  with automatic migration on startup and cleanup for revoked keys
- Disable uvicorn access log by default (query params out of terminals)
- New GET /api/export: JSON/CSV export of local data (offline, Excel BOM)
- Add docs/PRIVACY.md: full data-flow audit, outbound endpoint inventory,
  threat model, self-verification steps
- 6 new tests (host allowlist, keyring roundtrip, CSV)

tests/test_security.py

@@ -0,0 +1,89 @@
+"""Tests for local security hardening (host allowlist, CORS, keyring secrets, CSV export)."""
+
+import keyring
+
+from mi_fitness_mcp.api import _to_csv
+from mi_fitness_mcp.security import (
+    default_allowed_hosts,
+    delete_api_key_secret,
+    host_allowed,
+    load_api_key_secret,
+    store_api_key_secret,
+)
+
+
+def test_host_allowed_strips_ports():
+    allowed = default_allowed_hosts()
+    assert host_allowed("127.0.0.1:8321", allowed)
+    assert host_allowed("localhost:9999", allowed)
+    assert host_allowed("LOCALHOST", allowed)
+    assert host_allowed("[::1]:8321", allowed)
+
+
+def test_host_allowed_rejects_foreign_domains():
+    allowed = default_allowed_hosts()
+    # DNS 重绑定场景：外部域名解析到 127.0.0.1，但 Host 头仍是外部域名
+    assert not host_allowed("evil.example.com", allowed)
+    assert not host_allowed("evil.example.com:8321", allowed)
+    assert not host_allowed(None, allowed)
+    assert not host_allowed("", allowed)
+
+
+def test_host_allowed_env_override():
+    # monkeypatch env via keyring-free approach: direct set check
+    import os
+
+    old = os.environ.get("MI_FITNESS_ALLOWED_HOSTS")
+    try:
+        os.environ["MI_FITNESS_ALLOWED_HOSTS"] = "lanhost.local,*"
+        allowed = default_allowed_hosts()
+        assert host_allowed("lanhost.local:8321", allowed)
+        assert host_allowed("anything.com", allowed)  # * 放行
+    finally:
+        if old is None:
+            os.environ.pop("MI_FITNESS_ALLOWED_HOSTS", None)
+        else:
+            os.environ["MI_FITNESS_ALLOWED_HOSTS"] = old
+
+
+def test_api_key_secret_roundtrip(monkeypatch):
+    store = {}
+
+    monkeypatch.setattr(keyring, "set_password", lambda s, a, v: store.__setitem__((s, a), v))
+    monkeypatch.setattr(keyring, "get_password", lambda s, a: store.get((s, a)))
+    monkeypatch.setattr(
+        keyring,
+        "delete_password",
+        lambda s, a: store.pop((s, a), None),
+    )
+
+    api_key = "mif_sk_" + "a" * 40
+    assert store_api_key_secret(api_key, "V1:secret-token")
+    assert load_api_key_secret(api_key) == "V1:secret-token"
+    # 不同 Key 的存储隔离（账号名含 key 哈希）
+    other = "mif_sk_" + "b" * 40
+    assert load_api_key_secret(other) is None
+    delete_api_key_secret(api_key)
+    assert load_api_key_secret(api_key) is None
+
+
+def test_store_api_key_secret_keyring_failure(monkeypatch):
+    def boom(_s, _a, _v):
+        raise RuntimeError("no keyring backend")
+
+    monkeypatch.setattr(keyring, "set_password", boom)
+    assert not store_api_key_secret("mif_sk_x", "tok")
+    assert load_api_key_secret("mif_sk_x") is None
+
+
+def test_to_csv_flattens_and_adds_bom():
+    rows = [
+        {"date": "2026-08-30", "steps": 100, "stages": [{"stage": "deep", "minutes": 60}]},
+        {"date": "2026-08-31", "steps": None, "stages": []},
+    ]
+    csv_text = _to_csv(rows)
+    assert csv_text.startswith("\ufeff")
+    assert "date,steps,stages" in csv_text
+    # CSV 规范内层引号转义为两个引号
+    assert '"[{""stage"": ""deep"", ""minutes"": 60}]"' in csv_text
+    assert "2026-08-31" in csv_text