fix: widen engines.node to include Node.js 24 LTS (#24419)

Dependabot's npm updater now ships Node.js v24.14.1 (Active LTS
"Krypton"). The `engines.node` field in `site/package.json` and
`offlinedocs/package.json` restricted to `>=18.0.0 <23.0.0`, causing
`ERR_PNPM_UNSUPPORTED_ENGINE` failures when Dependabot tried to update
packages (e.g. the `axios` security update).

Widens the upper bound to `<25.0.0` so Node.js 24.x is accepted. The
project itself continues to use Node 22 via `flake.nix`.

Reference:
https://github.com/coder/coder/actions/runs/24482279340/job/71549366110

> [!NOTE]
> This PR was authored by Coder Agents.

offlinedocs/package.json

@@ -42,7 +42,7 @@
 	},
 	"engines": {
 		"npm": ">=9.0.0 <10.0.0",
-		"node": ">=18.0.0 <23.0.0"
+		"node": ">=18.0.0 <25.0.0"
 	},
 	"pnpm": {
 		"overrides": {

site/package.json

@@ -195,7 +195,7 @@
 	},
 	"engines": {
 		"pnpm": ">=10.0.0 <11.0.0",
-		"node": ">=18.0.0 <23.0.0"
+		"node": ">=18.0.0 <25.0.0"
 	},
 	"pnpm": {
 		"overrides": {