Fix iOS bottom sheet — use visibility+transform instead of display:none

iOS Safari doesn't recalculate height properly with display:none→block.
Switch to display:block!important + visibility:hidden + translateY(100%)
+ pointer-events:none for hidden state. This ensures iOS renders the
full sheet height before showing it. Also remove overflow:hidden from
base .user-menu that was clipping content.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/base.html

@@ -939,7 +939,6 @@
             box-shadow: var(--shadow-lg);
             min-width: 220px;
             z-index: 200;
-            overflow: hidden;
         }
 
         .user-menu.show {
@@ -958,23 +957,32 @@
             .user-menu-overlay.show { display: block; }
 
             .user-menu {
+                display: block !important;
                 position: fixed;
                 top: auto;
                 bottom: 0;
                 left: 0;
                 right: 0;
+                width: 100%;
                 min-width: 100%;
+                max-height: 80vh;
+                overflow-y: auto;
+                -webkit-overflow-scrolling: touch;
                 border-radius: 16px 16px 0 0;
                 border: none;
                 box-shadow: 0 -4px 20px rgba(0,0,0,0.15);
                 z-index: 9999;
                 padding-bottom: env(safe-area-inset-bottom, 16px);
+                visibility: hidden;
                 transform: translateY(100%);
-                transition: transform 0.25s ease-out;
+                transition: transform 0.25s ease-out, visibility 0s 0.25s;
+                pointer-events: none;
             }
             .user-menu.show {
-                display: block;
+                visibility: visible;
                 transform: translateY(0);
+                transition: transform 0.25s ease-out, visibility 0s 0s;
+                pointer-events: auto;
             }
             .user-menu-handle {
                 display: block;