Adds backend/src/utils/parseIntParam.ts with a shared parseIntParam
helper that writes a 400 'Invalid <label>' response and returns null on
non-numeric route params. Consolidates the parseInt + isNaN + 400 shape
that was inlined or duplicated across multiple routers.
Updated:
- routes/fleet.ts: replaced the local parseIdParam wrapper.
- routes/autoHeal.ts: replaced the local parsePolicyId wrapper.
- routes/notifications.ts: replaced parseRouteId wrapper plus an inline
notification-id site.
- routes/apiTokens.ts, routes/labels.ts, routes/registries.ts,
routes/scheduledTasks.ts, routes/users.ts: replaced inline copies.
Out of scope (route handlers without an existing isNaN check, kept
intentionally untouched to avoid introducing new 400 responses): alerts,
nodes, webhooks, and several user-routes handlers that rely on a
downstream 404 instead.
Closes#748
Anso