chore: cursor-blink on empty-state placeholders

Adds the cursor-blink class to "no X" / "select a Y" placeholders across
core (calendar popup, board preview, search preview, detail split, notifs)
and plugins (chat, email, gitea, slideshow). Visual consistency with the
rest of the pixel-font UI.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/plugins/chat/chat.js

@@ -307,7 +307,7 @@ async function openPickView() {
     const self = recipientCache.self;
     const others = tenants.filter(t => t.username !== self);
     if (!others.length) {
-        list.innerHTML = '<div class="px-3 py-3 text-[10px] text-t-dim font-pixel">no other users on the relay</div>';
+        list.innerHTML = '<div class="px-3 py-3 text-[10px] text-t-dim font-pixel cursor-blink">no other users on the relay</div>';
         return;
     }
     list.innerHTML = others.map(t => `