fix: bottom-nav-inner must be column not row — tabs stacked above buttons

flex-direction:row put the tab strip and icon buttons side-by-side,
both fighting for 100% width, making them overflow and appear huge.
Column stacks the Bibliothek/Entdecken tabs on top, icon row below.

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

styles.css

@@ -368,7 +368,7 @@ nav{flex:1;overflow-y:auto;padding:4px 10px}
   padding-bottom:env(safe-area-inset-bottom);
 }
 .bottom-nav-inner{
-  display:flex;flex-direction:row;align-items:stretch;
+  display:flex;flex-direction:column;align-items:stretch;
   height:100%;width:100%;
 }
 .bnav-item{