fix: prevent fight view scrolling on mobile with tab bar

All pages used h-[calc(100dvh-4rem)] which only subtracted the top
navbar but ignored the mobile tab bar's pb-14 bottom padding, causing
content to overflow and scroll. Changed all pages to h-full so they
fill the flex parent (main element) which already handles both the
navbar and tab bar spacing correctly.

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

frontend/src/pages/JoinBoutPage.vue

@@ -419,7 +419,7 @@ function handleSignOut() {
 </script>
 
 <template>
-  <div class="h-[calc(100dvh-4rem)] flex flex-col items-center justify-center px-6 overflow-hidden">
+  <div class="h-full flex flex-col items-center justify-center px-6 overflow-hidden">
     <div class="max-w-md w-full slide-up overflow-y-auto max-h-full py-4">
 
       <!-- STEP: LOGIN -->