chore: synchronize pending app/backend updates and repository hygiene

Includes current frontend and backend work in progress and removes generated artifacts from tracking to keep the repository clean for дальнейшая разработка.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/services/alert-engine/cooldown.ts

@@ -0,0 +1,22 @@
+import type { ApiAlertRule } from "../alerts-service.js"
+
+const COOLDOWN_MS: Record<ApiAlertRule["cooldown"], number> = {
+  "1м": 60_000,
+  "5м": 5 * 60_000,
+  "15м": 15 * 60_000,
+  "1ч": 60 * 60_000,
+  "4ч": 4 * 60 * 60_000,
+  "24ч": 24 * 60 * 60_000,
+}
+
+export function cooldownToMs(cd: ApiAlertRule["cooldown"]): number {
+  return COOLDOWN_MS[cd] ?? COOLDOWN_MS["5м"]
+}
+
+/** Можно ли отправить снова после lastIso (ISO) */
+export function isCooldownElapsed(lastFiredIso: string | null | undefined, cooldown: ApiAlertRule["cooldown"]): boolean {
+  if (!lastFiredIso?.trim()) return true
+  const t = Date.parse(lastFiredIso)
+  if (!Number.isFinite(t)) return true
+  return Date.now() - t >= cooldownToMs(cooldown)
+}