security: Remove hardcoded admin credentials from login page

CRITICAL SECURITY FIX:
- Remove display of default admin username and password from login.ctml
- Login page no longer advertises 'admin' / 'asteroid123' credentials

This was the security issue Fade mentioned during b612 deployment:
'the templates with the default passwords for sure need changing'

Addresses TODO item:
- Problem 4: Templates advertising default admin password ✅ FIXED

Ref: TODO.org line 29-30

template/login.ctml

@@ -37,11 +37,6 @@
             <button type="submit" class="btn btn-primary" style="width: 100%;">LOGIN</button>
           </div>
         </form>
-        <div class="panel" style="margin-top: 20px; text-align: center;">
-          <strong style="color: #ff6600;">Default Admin Credentials:</strong><br>
-          Username: <br><code style="color: #00ff00;">admin</code><br>
-          Password: <br><code style="color: #00ff00;">asteroid123</code>
-        </div>
       </div>
     </div>
   </div>