fix: update Deck Coach status label from LM Studio to Perplexity

ui/coach.html

@@ -23,7 +23,7 @@
             <div class="coach-status-items">
                 <div class="coach-status-item" id="status-llm">
                     <span class="status-dot status-unknown"></span>
-                    <span class="status-label">LM Studio</span>
+                    <span class="status-label">Perplexity</span>
                     <span class="status-value" id="status-llm-value">Checking...</span>
                 </div>
                 <div class="coach-status-item" id="status-embeddings">