pres_mgmt: redesign Session View, clean Presentation list, fix transitions

- session_view.svelte: replace flat <ul> with hero card layout
  - Name as <h1>, date/time chip (primary teal), room chip (tertiary indigo)
  - QR only rendered when URL is string (not true loading placeholder)
  - Skeleton pulse placeholders while LiveQuery resolves
  - Description in surface card with uppercase label
  - Accessible: aria labels, focus rings, aria-live on no-results section
- ae_comp__event_session_obj_li.svelte:
  - variant-soft-warning (Skeleton v3) -> preset-tonal-warning (v4)
  - Add transition-colors duration-200 to <tr> rows and session <a> links
- ae_comp__event_presentation_obj_li.svelte:
  - Remove debug breakpoint border colors (red/yellow/gray)
  - overflow-x-scroll -> overflow-x-auto
  - Remove heavy preset-filled-surface-400-600 from <ul> container
  - <li> cards: surface tokens, rounded-xl, shadow-sm, transition
  - <h4> title bar: bg-surface-100-900 with flex wrap layout
  - Code badge: hardcoded yellow -> preset-tonal-warning
  - Description <pre>: hardcoded bg-gray-100 -> bg-surface-100-900
- pres_mgmt/+page.svelte: 'no results' section
  - bg-yellow-100 + text-yellow-500 -> preset-tonal-warning
  - Search icon, aria-live, cleaner list in surface card
- [session_id]/+page.svelte: rounded-container-token (v3) -> rounded-xl

src/routes/events/ae_comp__event_session_obj_li.svelte

@@ -141,9 +141,9 @@
             <tbody>
                 {#each visible_session_obj_li as session_obj, index (session_obj.id || session_obj.event_session_id || session_obj.event_session_id_random || index)}
                     <tr
-                        class="relative"
+                        class="relative transition-colors duration-200"
                         class:opacity-50={session_obj?.hide}
-                        class:variant-soft-warning={!session_obj?.enable}
+                        class:preset-tonal-warning={!session_obj?.enable}
                     >
                         <td>
                             {#if session_obj?.alert && $ae_loc.trusted_access}
@@ -157,7 +157,7 @@
                                 <div class="flex items-center gap-2">
                                     <a
                                         href="/events/{session_obj?.event_id}/session/{session_obj?.event_session_id}"
-                                        class="flex flex-row gap-2 items-center font-bold text-lg hover:text-primary-500 text-left"
+                                        class="flex flex-row gap-2 items-center font-bold text-lg hover:text-primary-500 text-left transition-colors duration-200"
                                     >
                                         {#if session_obj?.hide}
                                             <EyeOff