fix(ui): add accessible name to the meetings search input (T7.5, FR-UX-4)

A placeholder isn't a reliable accessible name (it disappears on input
and isn't consistently exposed) — add an explicit aria-label.

src/lib/views/MeetingsList.svelte

@@ -46,7 +46,12 @@
 </script>
 
 <div class="wrap">
-  <input placeholder="Search meetings…" bind:value={query} oninput={onSearchInput} />
+  <input
+    placeholder="Search meetings…"
+    aria-label="Search meetings"
+    bind:value={query}
+    oninput={onSearchInput}
+  />
   {#if meetings.list.length === 0}
     <p class="muted">No meetings yet. Click ● Record to start.</p>
   {:else}