Make Login Modal full-screen on mobile devices

This change updates `components/login-modal.html` to remove layout constraints (`items-start`, `justify-center`, `max-h-modal-shell`) on mobile viewports (< lg) by prefixing them with `lg:`. This allows the modal to utilize the default full-screen behavior provided by the `.bv-modal` and `.modal-sheet` classes on smaller screens, matching the behavior of the Profile and Video modals. Desktop layout remains unchanged.

components/login-modal.html

@@ -1,6 +1,6 @@
 <div
   id="loginModal"
-  class="bv-modal hidden items-start justify-center"
+  class="bv-modal hidden lg:items-start lg:justify-center"
   role="dialog"
   aria-modal="true"
   aria-labelledby="loginModalTitle"
@@ -10,7 +10,7 @@
   <div class="bv-modal-backdrop" data-dismiss></div>
 
   <div
-    class="modal-sheet max-h-modal-shell flex min-h-0 flex-col overflow-hidden"
+    class="modal-sheet lg:max-h-modal-shell flex min-h-0 flex-col overflow-hidden"
     tabindex="-1"
   >
     <!-- Header with the special exit button (unchanged) -->