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_session_view.svelte

@@ -16,6 +16,8 @@
     import Launcher_presentation_view from './launcher_presentation_view.svelte';
     import Launcher_presenter_view from './launcher_presenter_view.svelte';
     import Launcher_presenter_view_posters from './launcher_presenter_view_posters.svelte';
+    // WHY: Poster sessions get a dedicated card-grid view optimised for touch/PWA use.
+    import Launcher_session_view_posters from './launcher_session_view_posters.svelte';
 
     import { liveQuery } from 'dexie';
     // import { core_func } from '$lib/ae_core_functions';
@@ -163,6 +165,10 @@
     {/if}
 
     {#if $lq__event_session_obj && $lq__event_session_obj.event_session_id}
+        {#if type_code === 'poster'}
+            <!-- WHY: Poster sessions use a dedicated touch-first card-grid layout. -->
+            <Launcher_session_view_posters {slct__event_session_id} {log_lvl} />
+        {:else}
         <!--
             Session header: flex-col keeps datetime and name on separate rows so
             the header height is predictable regardless of session name length.
@@ -462,6 +468,7 @@
                 <p>No presentations available to display.</p>
             {/if}
         </section>
+        {/if}<!-- end type_code !== 'poster' -->
     {:else}
         <span class="fas fa-spinner fa-spin"></span>
         No session selected