feat(sms): verify_code try-both 遍历启用的 fallback 链

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/integrations/sms/__init__.py

@@ -56,5 +56,17 @@ def send_code(phone: str) -> SendResult:
 
 
 def verify_code(phone: str, code: str) -> bool:
-    """校验：委托当前主 provider（try-both 在 Task 5 加）。"""
-    return _primary().verify_code(phone, code)
+    """校验：try-both，遍历「启用的 fallback 链」（主→备），任一命中即 True。
+
+    码只存在实际发码那家（fallback 前主已 pop 掉自己的码），另一家 rec is None 即 False、
+    不误判、不累加其防爆破计数。关闭 fallback 时链中只有主，备完全不参与。
+    """
+    chain = [_primary()]
+    fb = _fallback()
+    if fb is not None:
+        chain.append(fb)
+    for prov in chain:
+        if prov.verify_code(phone, code):   # Mode B：纯本地内存比对，不联网
+            logger.info("[SMS] verify hit provider=%s", _NAME[prov])
+            return True
+    return False

tests/test_sms_fallback.py

@@ -92,3 +92,51 @@ def test_send_code_backup_also_fails_raises_backup_error(monkeypatch):
     with pytest.raises(SmsError) as ei:
         sms.send_code(PHONE)
     assert "创蓝" in str(ei.value)
+
+
+def test_verify_hits_primary_without_touching_backup(monkeypatch):
+    calls = []
+    monkeypatch.setattr(settings, "SMS_PROVIDER", "jiguang")
+    monkeypatch.setattr(settings, "SMS_FALLBACK_PROVIDER", "chuanglan")
+    monkeypatch.setattr(jiguang, "verify_code",
+                        lambda p, c: (calls.append("jiguang"), True)[1])
+    monkeypatch.setattr(chuanglan, "verify_code",
+                        lambda p, c: (calls.append("chuanglan"), True)[1])
+
+    assert sms.verify_code(PHONE, "123456") is True
+    assert calls == ["jiguang"]
+
+
+def test_verify_falls_through_to_backup(monkeypatch):
+    calls = []
+    monkeypatch.setattr(settings, "SMS_PROVIDER", "jiguang")
+    monkeypatch.setattr(settings, "SMS_FALLBACK_PROVIDER", "chuanglan")
+    monkeypatch.setattr(jiguang, "verify_code",
+                        lambda p, c: (calls.append("jiguang"), False)[1])
+    monkeypatch.setattr(chuanglan, "verify_code",
+                        lambda p, c: (calls.append("chuanglan"), True)[1])
+
+    assert sms.verify_code(PHONE, "123456") is True
+    assert calls == ["jiguang", "chuanglan"]
+
+
+def test_verify_all_miss_returns_false(monkeypatch):
+    monkeypatch.setattr(settings, "SMS_PROVIDER", "jiguang")
+    monkeypatch.setattr(settings, "SMS_FALLBACK_PROVIDER", "chuanglan")
+    monkeypatch.setattr(jiguang, "verify_code", lambda p, c: False)
+    monkeypatch.setattr(chuanglan, "verify_code", lambda p, c: False)
+
+    assert sms.verify_code(PHONE, "123456") is False
+
+
+def test_verify_backup_not_touched_when_fallback_off(monkeypatch):
+    calls = []
+    monkeypatch.setattr(settings, "SMS_PROVIDER", "jiguang")
+    monkeypatch.setattr(settings, "SMS_FALLBACK_PROVIDER", "")
+    monkeypatch.setattr(jiguang, "verify_code",
+                        lambda p, c: (calls.append("jiguang"), False)[1])
+    monkeypatch.setattr(chuanglan, "verify_code",
+                        lambda p, c: (calls.append("chuanglan"), True)[1])
+
+    assert sms.verify_code(PHONE, "123456") is False
+    assert calls == ["jiguang"]