Serve published decks from a trailing-slash URL so assets load

A deck served at /p/:token (no trailing slash) made the browser resolve its
relative asset references (main_files/... CSS+JS) against /p/, 404ing them —
so the deck rendered as unstyled HTML with no reveal.js. Publish links now end
in a slash, and the bare /p/:token URL 301-redirects to /p/:token/, so relative
assets resolve under /p/:token/ and load correctly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/web/app/src/Features/PublishedPresentation/PublishedPresentationController.mjs

@@ -6,7 +6,9 @@ import SessionManager from '../Authentication/SessionManager.mjs'
 import PublishedPresentationManager from './PublishedPresentationManager.mjs'
 
 function _publicUrl(token) {
-  return `${Settings.siteUrl}/p/${token}`
+  // Trailing slash so the deck's relative asset paths (e.g. main_files/...)
+  // resolve under /p/:token/ rather than /p/.
+  return `${Settings.siteUrl}/p/${token}/`
 }
 
 function _serialize(record) {
@@ -63,6 +65,12 @@ async function serve(req, res) {
   const record = await PublishedPresentationManager.promises.getByToken(token)
   if (!record) return res.status(404).send('Presentation not found')
 
+  // Normalise the bare token URL to a trailing slash so the deck's relative
+  // asset references resolve under /p/:token/ instead of /p/.
+  if (!req.params.file && !req.path.endsWith('/')) {
+    return res.redirect(301, `/p/${encodeURIComponent(token)}/`)
+  }
+
   if (
     record.visibility === 'private' &&
     !SessionManager.getLoggedInUserId(req.session)