Remove dead code from profile and password proxy systems

Strip ~966 lines of unused code after transitioning to cookie-only
auth: profile CRUD handlers, encryption helpers, username/password
proxy launcher, proxy check/version handlers, dead preload methods,
orphaned CSS (modals, profiles, nav tabs, collapsible sections),
unused DOM elements and renderer functions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

index.html

@@ -78,12 +78,6 @@
         </div>
     </div>
 
-    <!-- Hidden elements for device details display -->
-    <div style="display: none;">
-        <div id="deviceDetails"></div>
-        <div id="mainContent"></div>
-    </div>
-
     <script src="renderer.js"></script>
 </body>
 </html>