fix(ui): show a loading state for the meetings list (T7.1, FR-UX-1)

meetings.loading existed in the store but nothing read it — the list
briefly showed "No meetings yet" on first load before data arrived.

src/lib/views/MeetingsList.svelte

@@ -52,7 +52,9 @@
     bind:value={query}
     oninput={onSearchInput}
   />
-  {#if meetings.list.length === 0}
+  {#if meetings.list.length === 0 && meetings.loading}
+    <p class="muted">Loading meetings…</p>
+  {:else if meetings.list.length === 0}
     <p class="muted">No meetings yet. Click ● Record to start.</p>
   {:else}
     <ul>