f023e38fdc
Replace all monitor package-level mutable state with Engine struct. All state (liveState, logStore, histories, tokenIndex, HTTP clients) is now encapsulated in Engine, created via NewEngine(store). Key changes: - Engine struct holds all monitor state with proper mutex protection - Engine.Start(ctx) and monitorRoutine respect context cancellation for graceful shutdown — no more leaked goroutines - cluster.runFollowerLoop also respects context for clean exit - Token index (map[string]int) for O(1) push heartbeat lookup, replacing O(n) linear scan through LiveState - UpdateSiteConfig preserves 8 runtime fields instead of copying 17 config fields individually - triggerAlert goroutines get 30s timeout context - All consumers (TUI, server, cluster, main) receive *Engine via constructor/parameter — no package-level state access - main.go creates context.WithCancel, passes to engine and cluster First test suite: 12 tests across store and alert packages - Store: CRUD for sites/alerts/users, push token generation, import/export round-trip, check history persistence - Alert: Discord/Slack/Webhook payload format, HTTP 4xx error propagation, Ntfy headers, unknown provider returns nil