feat(launcher): dedicated Digital Poster session card-grid view

Create launcher_session_view_posters.svelte — a touch-first card-grid
layout for Digital Poster sessions, designed for tablet/phone PWA use.

Layout:
- 1 column on mobile, 2 on sm, 3 on xl
- Each poster card: title (line-clamp-3) + presenter name/affiliation +
  'Open Poster' action button at card bottom
- Poster code (or 1-based index fallback) badge in top-right corner
- Card active:scale-[0.98] for tactile touch press feedback
- Sticky compact session header strip with name, code, and poster count
- Optional 'Session Resources' strip for rare session-level files
- overflow-y-auto + grow so the grid scrolls; header strip stays fixed

Integration:
- launcher_session_view.svelte: import + delegate when type_code==='poster'
- launcher_file_cont.svelte: min-w-96 → w-full on poster button so it
  fills its container (card or list row) without overflow on small screens
- WS open/close/zoom command pipeline unchanged (all in launcher_file_cont
  and +layout.svelte which were not modified for the WS paths)

src/routes/events/[event_id]/(launcher)/launcher_file_cont.svelte

@@ -258,7 +258,7 @@
             <AE_Comp_Hosted_Files_Download_Button
                 hosted_file_id={event_file_id}
                 hosted_file_obj={event_file_obj}
-                classes="btn btn-sm md:btn-md lg:btn-lg preset-tonal-primary border border-primary-500 min-w-96"
+                classes="btn btn-sm md:btn-md lg:btn-lg preset-tonal-primary border border-primary-500 w-full"
                 click={() => {
                     modal__open_event_file_id = event_file_id;
                     modal__event_file_obj = event_file_obj;