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/index.php

@@ -1229,7 +1229,7 @@ if (str_starts_with($route, '/api/')) {
             </div>
             <div id="board-preview-empty" class="flex-1 flex flex-col items-center justify-center text-t-dim">
                 <i class="ph ph-article text-3xl mb-2"></i>
-                <p class="font-pixel text-[10px]">click a card to preview</p>
+                <p class="font-pixel text-[10px] cursor-blink">click a card to preview</p>
             </div>
             <div id="board-preview-content" class="hidden flex-1 flex flex-col min-h-0">
                 <div id="board-preview-body" class="flex-1 overflow-y-auto p-5 prose text-sm text-t-text"></div>
@@ -1826,7 +1826,7 @@ if (str_starts_with($route, '/api/')) {
             <div class="flex flex-1 min-h-0">
                 <div id="search-results" class="overflow-y-auto w-2/5 min-w-[220px] border-r border-t-border"></div>
                 <div class="flex-1 overflow-y-auto p-5">
-                    <div id="search-preview-empty" class="flex flex-col items-center justify-center h-full text-t-dim"><i class="ph ph-article text-3xl mb-2"></i><p class="font-pixel text-[10px]">select a card</p></div>
+                    <div id="search-preview-empty" class="flex flex-col items-center justify-center h-full text-t-dim"><i class="ph ph-article text-3xl mb-2"></i><p class="font-pixel text-[10px] cursor-blink">select a card</p></div>
                     <div id="search-preview-content" class="hidden">
                         <div class="card-bar w-16 mb-4 rounded-sm" id="search-preview-color"></div>
                         <h2 id="search-preview-title" class="font-pixel text-t-bright text-sm mb-4 leading-relaxed"></h2>