fix(frontend): fix i18n and runtime error in EndpointList

Fix hardcoded English labels in cache strategy display and prevent runtime
error when filePatterns is undefined.

Changes:
- Replace hardcoded "TTL:", "Max:", "Patterns:" with formatMessage calls
- Add optional chaining for filePatterns.length to prevent undefined error
- Add "filePatterns" i18n key to en/zh api-settings.json

ccw/frontend/src/components/api-settings/EndpointList.tsx

@@ -92,10 +92,10 @@ function EndpointCard({
           )}
           {endpoint.cacheStrategy.enabled && (
             <div className="flex items-center gap-3 mt-2 text-xs text-muted-foreground">
-              <span>TTL: {endpoint.cacheStrategy.ttlMinutes}m</span>
-              <span>Max: {endpoint.cacheStrategy.maxSizeKB}KB</span>
-              {endpoint.cacheStrategy.filePatterns.length > 0 && (
-                <span>Patterns: {endpoint.cacheStrategy.filePatterns.length}</span>
+              <span>{formatMessage({ id: 'apiSettings.endpoints.cacheTTL' })}: {endpoint.cacheStrategy.ttlMinutes}m</span>
+              <span>{formatMessage({ id: 'apiSettings.endpoints.cacheMaxSize' })}: {endpoint.cacheStrategy.maxSizeKB}KB</span>
+              {(endpoint.cacheStrategy.filePatterns?.length || 0) > 0 && (
+                <span>{formatMessage({ id: 'apiSettings.endpoints.filePatterns' })}: {endpoint.cacheStrategy.filePatterns?.length || 0}</span>
               )}
             </div>
           )}

ccw/frontend/src/locales/en/api-settings.json

@@ -167,6 +167,7 @@
     "enableContextCaching": "Enable context caching",
     "cacheTTL": "Cache TTL (minutes)",
     "cacheMaxSize": "Max Size (KB)",
+    "filePatterns": "Patterns",
     "autoCachePatterns": "Auto-cache patterns",
     "filePatternsHint": "Comma-separated glob patterns (e.g., *.md,*.ts)",
     "enabled": "Enabled",

ccw/frontend/src/locales/zh/api-settings.json

@@ -164,6 +164,7 @@
     "enableContextCaching": "启用上下文缓存",
     "cacheTTL": "缓存 TTL（分钟）",
     "cacheMaxSize": "最大大小（KB）",
+    "filePatterns": "模式数",
     "autoCachePatterns": "自动缓存模式",
     "filePatternsHint": "逗号分隔的 glob 模式（例如：*.md,*.ts）",
     "enabled": "已启用",