UI: Font Awesome icons, Material touches, 3-line collapse button

Swap all emoji icons for Font Awesome (sidebar, homepage tiles, profile/chat/
list/settings/relay actions); add Roboto font + card elevation hover for a
Material feel. Replace the bottom 'Collapse' pill with a 3-line (fa-bars) toggle
in the sidebar header; remove the old collapse pill CSS/JS. Copy buttons toggle
FA check/copy via innerHTML. Plain text status (✓/✗) and back arrows kept.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

manager/templates/chat.html

@@ -51,11 +51,11 @@
   <div class="chat-head">
     <span class="title">{{ chat_name }}</span>
     <button class="btn btn-ghost" style="padding:4px 12px;font-size:12px;"
-            onclick="loadMessages(true)">↻ Refresh</button>
+            onclick="loadMessages(true)"><i class="fa-solid fa-rotate-right"></i> Refresh</button>
   </div>
 
   {% if is_channel %}
-  <div class="chat-banner">📢 Channel — messages you send here broadcast to all subscribers.</div>
+  <div class="chat-banner"><i class="fa-solid fa-bullhorn"></i> Channel — messages you send here broadcast to all subscribers.</div>
   {% endif %}
 
   <div class="chat-log" id="chat-log">