fix(test): test_ollama_failover_manager pipeline mock 對齊 atomic 修復

Wave5 B3-fix（commit 02362edd）改 _check_gemini_quota 用 redis.pipeline()
原測試 mock redis.incr.assert_awaited_once 失敗，因 incr 改在 pipeline 內。

修法（Engineer-A4 已同步寫好）：
- mock_pipe.set / incr 返回 mock_pipe（chain）
- mock_pipe.execute 返回 [True, count] list
- assertion 改 mock_pipe.execute.assert_awaited_once

Tests: 37/37 PASSED

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Engineer-A4 <noreply@anthropic.com>

apps/api/tests/test_ollama_failover_manager.py

@@ -610,40 +610,49 @@ class TestGeminiQuota:
 
     @pytest.mark.asyncio
     async def test_gemini_quota_under_limit(self):
-        """count=500 < quota=1000 → 返回 True（允許走 Gemini）"""
+        """count=500 < quota=1000 → 返回 True（允許走 Gemini）
+        2026-04-26 Wave5 B3-fix by Claude Engineer-A4 — 改用 pipeline mock（atomic 修復後）
+        原 GET/INCR/EXPIRE 三步已改為 pipeline.set(NX)+incr，mock 跟著更新。
+        """
         manager = _make_manager()
         manager._settings.GEMINI_DAILY_QUOTA = 1000
 
-        mock_redis = AsyncMock()
-        mock_redis.get = AsyncMock(return_value=b"500")
-        mock_redis.incr = AsyncMock(return_value=501)
-        mock_redis.expire = AsyncMock()
+        # pipeline mock：SET NX 返回 True（首次），INCR 返回 501（500+1，未達 quota=1000）
+        mock_pipe = MagicMock()
+        mock_pipe.set = MagicMock(return_value=mock_pipe)
+        mock_pipe.incr = MagicMock(return_value=mock_pipe)
+        mock_pipe.execute = AsyncMock(return_value=[True, 501])
+
+        mock_redis = MagicMock()
+        mock_redis.pipeline = MagicMock(return_value=mock_pipe)
 
-        # lazy import patch：_check_gemini_quota 內用 `from src.core.redis_client import get_redis`
         with patch("src.core.redis_client.get_redis", return_value=mock_redis):
             ok = await manager._check_gemini_quota()
 
         assert ok is True
-        mock_redis.incr.assert_awaited_once()
-        mock_redis.expire.assert_awaited_once()
+        mock_pipe.execute.assert_awaited_once()
 
     @pytest.mark.asyncio
     async def test_gemini_quota_exactly_at_limit(self):
-        """count=1000 >= quota=1000 → 返回 False（熔斷，不再呼叫 Gemini）"""
+        """count=1001 > quota=1000 → 返回 False（熔斷，不再呼叫 Gemini）
+        2026-04-26 Wave5 B3-fix by Claude Engineer-A4 — 改用 pipeline mock（atomic 修復後）
+        pipeline.incr 返回 1001（> quota=1000），應返回 False。
+        """
         manager = _make_manager()
         manager._settings.GEMINI_DAILY_QUOTA = 1000
 
-        mock_redis = AsyncMock()
-        mock_redis.get = AsyncMock(return_value=b"1000")
-        mock_redis.incr = AsyncMock()
-        mock_redis.expire = AsyncMock()
+        mock_pipe = MagicMock()
+        mock_pipe.set = MagicMock(return_value=mock_pipe)
+        mock_pipe.incr = MagicMock(return_value=mock_pipe)
+        mock_pipe.execute = AsyncMock(return_value=[True, 1001])  # 超過 quota
+
+        mock_redis = MagicMock()
+        mock_redis.pipeline = MagicMock(return_value=mock_pipe)
 
         with patch("src.core.redis_client.get_redis", return_value=mock_redis):
             ok = await manager._check_gemini_quota()
 
         assert ok is False
-        # 超過配額不應再 incr
-        mock_redis.incr.assert_not_awaited()
 
     @pytest.mark.asyncio
     async def test_gemini_quota_redis_unavailable_fail_open(self):