fix(api): 修復 34 個 Ruff lint 錯誤

- 自動修復 import 排序、unused imports
- 手動修復 raise from、isinstance union、unused variable
- scripts/ 暫時保留 (非 CI 阻擋)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/tests/test_nvidia_provider.py

@@ -6,7 +6,6 @@ NVIDIA Provider Tests - ADR-036
 注意: 這些是單元測試，不需要真實的 NVIDIA API Key
 """
 
-import json
 
 import pytest
 
@@ -407,7 +406,7 @@ class TestAIRouterNvidiaIntegration:
 
     def test_tool_calling_route(self):
         """測試 Tool Calling 路由"""
-        from src.services.ai_router import get_ai_router, AIProvider, reset_ai_router
+        from src.services.ai_router import AIProvider, get_ai_router, reset_ai_router
 
         reset_ai_router()
         router = get_ai_router()
@@ -425,7 +424,7 @@ class TestAIRouterNvidiaIntegration:
 
     def test_existing_routing_not_affected(self):
         """測試現有路由規則不受影響"""
-        from src.services.ai_router import get_ai_router, AIProvider, reset_ai_router
+        from src.services.ai_router import AIProvider, get_ai_router, reset_ai_router
 
         reset_ai_router()
         router = get_ai_router()
@@ -568,9 +567,9 @@ class TestPrometheusMetrics:
     def test_metrics_defined(self):
         """測試 Prometheus Metrics 已定義"""
         from src.services.nvidia_provider import (
-            NVIDIA_REQUESTS_TOTAL,
-            NVIDIA_LATENCY_HISTOGRAM,
             NVIDIA_CIRCUIT_BREAKER_STATE,
+            NVIDIA_LATENCY_HISTOGRAM,
+            NVIDIA_REQUESTS_TOTAL,
         )
 
         assert NVIDIA_REQUESTS_TOTAL is not None
@@ -593,8 +592,8 @@ class TestExponentialBackoff:
         """測試退避常數已定義"""
         from src.services.nvidia_provider import (
             RETRY_BASE_DELAY,
-            RETRY_MAX_DELAY,
             RETRY_EXPONENTIAL_BASE,
+            RETRY_MAX_DELAY,
         )
 
         assert RETRY_BASE_DELAY == 1.0