feat(ops): 优化健康评分算法和智能诊断机制

- 采用分层加权评分（业务70% + 基础设施30%），避免重复扣分
- 新增延迟诊断（P99 > 2s critical, > 1s warning）
- 新增资源诊断（CPU/内存/DB/Redis状态）
- 调整诊断阈值（上游错误率5% critical，请求错误率3% critical）
- 为每个诊断项添加可操作建议
- 添加完整的单元测试覆盖（30+测试用例）
- 完善中英文国际化文本

frontend/src/i18n/locales/en.ts

@@ -1928,22 +1928,62 @@ export default {
         footer: 'Automated diagnostic suggestions based on current metrics',
         idle: 'System is currently idle',
         idleImpact: 'No active traffic',
+        // Resource diagnostics
+        dbDown: 'Database connection failed',
+        dbDownImpact: 'All database operations will fail',
+        dbDownAction: 'Check database service status, network connectivity, and connection configuration',
+        redisDown: 'Redis connection failed',
+        redisDownImpact: 'Cache functionality degraded, performance may decline',
+        redisDownAction: 'Check Redis service status and network connectivity',
+        cpuCritical: 'CPU usage critically high ({usage}%)',
+        cpuCriticalImpact: 'System response slowing, may affect all requests',
+        cpuCriticalAction: 'Check CPU-intensive tasks, consider scaling or code optimization',
+        cpuHigh: 'CPU usage elevated ({usage}%)',
+        cpuHighImpact: 'System load is high, needs attention',
+        cpuHighAction: 'Monitor CPU trends, prepare scaling plan',
+        memoryCritical: 'Memory usage critically high ({usage}%)',
+        memoryCriticalImpact: 'May trigger OOM, system stability threatened',
+        memoryCriticalAction: 'Check for memory leaks, consider increasing memory or optimizing usage',
+        memoryHigh: 'Memory usage elevated ({usage}%)',
+        memoryHighImpact: 'Memory pressure is high, needs attention',
+        memoryHighAction: 'Monitor memory trends, check for memory leaks',
+        // Latency diagnostics
+        latencyCritical: 'Response latency critically high ({latency}ms)',
+        latencyCriticalImpact: 'User experience extremely poor, many requests timing out',
+        latencyCriticalAction: 'Check slow queries, database indexes, network latency, and upstream services',
+        latencyHigh: 'Response latency elevated ({latency}ms)',
+        latencyHighImpact: 'User experience degraded, needs optimization',
+        latencyHighAction: 'Analyze slow request logs, optimize database queries and business logic',
+        ttftHigh: 'Time to first byte elevated ({ttft}ms)',
+        ttftHighImpact: 'User perceived latency increased',
+        ttftHighAction: 'Optimize request processing flow, reduce pre-processing time',
+        // Error rate diagnostics
         upstreamCritical: 'Upstream error rate critically high ({rate}%)',
         upstreamCriticalImpact: 'May affect many user requests',
+        upstreamCriticalAction: 'Check upstream service health, enable fallback strategies',
         upstreamHigh: 'Upstream error rate elevated ({rate}%)',
         upstreamHighImpact: 'Recommend checking upstream service status',
-        slaCritical: 'SLA critically below target ({sla}%)',
-        slaCriticalImpact: 'User experience severely degraded',
-        slaLow: 'SLA below target ({sla}%)',
-        slaLowImpact: 'Service quality needs attention',
+        upstreamHighAction: 'Contact upstream service team, prepare fallback plan',
         errorHigh: 'Error rate too high ({rate}%)',
         errorHighImpact: 'Many requests failing',
+        errorHighAction: 'Check error logs, identify root cause, urgent fix required',
         errorElevated: 'Error rate elevated ({rate}%)',
         errorElevatedImpact: 'Recommend checking error logs',
+        errorElevatedAction: 'Analyze error types and distribution, create fix plan',
+        // SLA diagnostics
+        slaCritical: 'SLA critically below target ({sla}%)',
+        slaCriticalImpact: 'User experience severely degraded',
+        slaCriticalAction: 'Urgently investigate errors and latency, consider rate limiting',
+        slaLow: 'SLA below target ({sla}%)',
+        slaLowImpact: 'Service quality needs attention',
+        slaLowAction: 'Analyze SLA decline causes, optimize system performance',
+        // Health score diagnostics
         healthCritical: 'Overall health score critically low ({score})',
         healthCriticalImpact: 'Multiple metrics may be degraded; prioritize error rate and latency investigation',
+        healthCriticalAction: 'Comprehensive system check, prioritize critical-level issues',
         healthLow: 'Overall health score low ({score})',
         healthLowImpact: 'May indicate minor instability; monitor SLA and error rates',
+        healthLowAction: 'Monitor metric trends, prevent issue escalation',
         healthy: 'All system metrics normal',
         healthyImpact: 'Service running stable'
       },