chore: decrease preview link validity to 5 minutes

Reduces the preview link time-to-live from 24 hours to 5 minutes for improved security. Updates related user-facing message in the dashboard editor to reflect this change.

app.config.ts

@@ -8,7 +8,7 @@ export default defineAppConfig({
   blog: 'https://sink.cool/blog',
   description: 'A Simple / Speedy / Secure Link Shortener with Analytics, 100% run on Cloudflare.',
   image: 'https://sink.cool/banner.png',
-  previewTTL: 24 * 3600, // 24h
+  previewTTL: 300, // 5 minutes
   slugRegex: /^[a-z0-9]+(?:-[a-z0-9]+)*$/i,
   reserveSlug: [
     'dashboard',

components/dashboard/links/Editor.vue

@@ -147,7 +147,7 @@ const { previewMode } = useRuntimeConfig().public
         v-if="previewMode"
         class="text-sm text-muted-foreground"
       >
-        The preview mode link is valid for up to 24 hours.
+        The preview mode link is valid for up to 5 minutes.
       </p>
       <AutoForm
         class="px-2 space-y-2 overflow-y-auto"