refactor(ops): 优化文案显示

- TTFT 定义统一改为"首 Token"/"First Token"(而非"首字节"/"first byte")
- 请求时长卡片标题去掉"（毫秒）"/"(ms)"后缀

frontend/src/i18n/locales/en.ts

@@ -1925,7 +1925,7 @@ export default {
       errors: 'Errors',
       errorRate: 'error_rate:',
       upstreamRate: 'upstream_rate:',
-      latencyDuration: 'Request Duration (ms)',
+      latencyDuration: 'Request Duration',
       ttftLabel: 'TTFT (first_token_ms)',
       p50: 'p50:',
       p90: 'p90:',
@@ -2590,7 +2590,7 @@ export default {
         errors: 'Error statistics, including total errors, error rate, and upstream error rate.',
         upstreamErrors: 'Upstream error statistics, excluding rate limit errors (429/529).',
         latency: 'Request duration statistics, including p50, p90, p95, p99 percentiles.',
-        ttft: 'Time To First Token, measuring the speed of first byte return in streaming responses.',
+        ttft: 'Time To First Token, measuring the speed of first token return in streaming responses.',
         health: 'System health score (0-100), considering SLA, error rate, and resource usage.'
       },
       charts: {