feat(telemetry): add comprehensive Prometheus metrics and expand dashboard with system, API, ML, and Node.js runtime sections

apps/api/src/lib/telemetry.ts

@@ -44,6 +44,14 @@ export const diagnosisCounter = new Counter({
   registers: [registry],
 });
 
+export const diagnosisUploadSize = new Histogram({
+  name: 'zeavis_api_diagnosis_upload_bytes',
+  help: 'Distribution of uploaded diagnosis image sizes in bytes',
+  labelNames: ['status'] as const,
+  buckets: [1024, 51200, 102400, 204800, 512000, 1048576, 2097152, 5242880],
+  registers: [registry],
+});
+
 export const authCounter = new Counter({
   name: 'zeavis_api_auth_operations_total',
   help: 'Total authentication operations (login, register, refresh)',
@@ -51,6 +59,43 @@ export const authCounter = new Counter({
   registers: [registry],
 });
 
+export const diseaseCatalogRequests = new Counter({
+  name: 'zeavis_api_disease_catalog_requests_total',
+  help: 'Total disease catalog page views',
+  labelNames: ['type'] as const,  // 'list' | 'detail'
+  registers: [registry],
+});
+
+export const expertReviewCounter = new Counter({
+  name: 'zeavis_api_expert_reviews_total',
+  help: 'Total expert reviews submitted',
+  labelNames: ['verdict'] as const,  // 'verified' | 'corrected'
+  registers: [registry],
+});
+
+export const dbQueryDuration = new Histogram({
+  name: 'zeavis_api_db_query_duration_seconds',
+  help: 'Histogram of database query durations',
+  labelNames: ['operation'] as const,
+  buckets: [0.001, 0.005, 0.01, 0.05, 0.1, 0.25, 0.5, 1],
+  registers: [registry],
+});
+
+export const imageModelInferenceDuration = new Histogram({
+  name: 'zeavis_api_ml_inference_duration_seconds',
+  help: 'Histogram of ML model inference durations (via API->ML service)',
+  labelNames: ['result'] as const,  // 'success' | 'failure'
+  buckets: [0.05, 0.1, 0.25, 0.5, 0.75, 1, 2, 5, 10],
+  registers: [registry],
+});
+
+export const mlServiceRequests = new Counter({
+  name: 'zeavis_api_ml_service_requests_total',
+  help: 'Total requests forwarded to ML service',
+  labelNames: ['status'] as const,  // 'success' | 'error'
+  registers: [registry],
+});
+
 // ── Export ──────────────────────────────────────────────
 
 export function getMetricsContentType(): string {