Phase 1: lock cron, reload chaud, argon2, providers, IMDb lookup, cache LRU, /health, /metrics, rate limit, UI dark, biome

lib/metrics.js

@@ -0,0 +1,46 @@
+// Prometheus metrics. Reusable counters/histograms for the API + cache.
+
+import { Counter, collectDefaultMetrics, Gauge, Histogram, Registry } from 'prom-client';
+
+export const registry = new Registry();
+collectDefaultMetrics({ register: registry });
+
+export const httpRequests = new Counter({
+  name: 'http_requests_total',
+  help: 'Total HTTP requests',
+  labelNames: ['method', 'route', 'status'],
+  registers: [registry],
+});
+
+export const httpDuration = new Histogram({
+  name: 'http_request_duration_seconds',
+  help: 'HTTP request duration in seconds',
+  labelNames: ['method', 'route', 'status'],
+  buckets: [0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 2, 5],
+  registers: [registry],
+});
+
+export const searchCacheHits = new Counter({
+  name: 'search_cache_hits_total',
+  help: 'Number of search results served from the LRU cache',
+  registers: [registry],
+});
+
+export const searchCacheMisses = new Counter({
+  name: 'search_cache_misses_total',
+  help: 'Number of search requests that bypassed the cache',
+  registers: [registry],
+});
+
+export const imdbRatingsCount = new Gauge({
+  name: 'imdb_ratings_total',
+  help: 'Number of IMDb ratings currently loaded in memory',
+  registers: [registry],
+});
+
+export const searchWorkers = new Gauge({
+  name: 'search_workers',
+  help: 'Number of active search workers per type',
+  labelNames: ['type'],
+  registers: [registry],
+});