fix: sidebar profile always visible — only .sb-nav scrolls, .sb-foot pinned at bottom

frontend/css/ls.css

@@ -258,18 +258,15 @@ body {
   position: sticky;
   top: 0;
   height: 100vh;
-  overflow-y: auto;
+  overflow: hidden;          /* sidebar itself does NOT scroll */
-  overflow-x: hidden;
   display: flex;
   flex-direction: column;
   background: rgba(238,242,255,0.94);
   backdrop-filter: blur(28px);
   border-right: 1.5px solid var(--border);
-  padding: 0 10px 16px;
+  padding: 0 10px 0;
   z-index: 50;
-  scrollbar-width: none;
 }
-.app-layout > .sidebar::-webkit-scrollbar { display: none; }
 
 .sb-brand {
   display: flex;
@@ -297,7 +294,12 @@ body {
   flex-direction: column;
   gap: 2px;
   flex: 1;
+  min-height: 0;             /* allows flex child to shrink below content size */
+  overflow-y: auto;
+  overflow-x: hidden;
+  scrollbar-width: none;
 }
+.sb-nav::-webkit-scrollbar { display: none; }
 
 .sb-link, a.sb-link, button.sb-link {
   display: flex;
@@ -399,9 +401,10 @@ body {
 }
 
 .sb-foot {
-  padding-top: 10px;
+  padding: 10px 0 16px;
   border-top: 1px solid var(--border);
   margin-top: 6px;
+  flex-shrink: 0;            /* never shrink — always visible at bottom */
 }
 
 .sb-user-row {

js/sidebar.js

@@ -71,7 +71,7 @@
       ${L('/gradebook',     'table',        'Журнал',       { cls: 'sb-teacher-only', hidden: !isTch })}
       ${L('/admin',         'settings',     'Управление',   { id: 'btn-admin', hidden: !isTch })}
     </nav>
-    <div style="padding:4px 2px">
+    <div style="padding:4px 2px;flex-shrink:0">
       ${isStu ? '<button class="sb-link" id="btn-join" style="display:none" onclick="typeof openJoinModal!==\'undefined\'&&openJoinModal()"><i data-lucide="user-plus" class="sb-icon"></i><span class="sb-lbl">Вступить в класс</span></button>' : ''}
       <div id="notif-wrap">
         <button class="sb-link" id="notif-btn" onclick="LS.notif?.toggle()">