fix: AddToMenu open-upward override for mobile (#575)

* debug: add console logs to AddToMenu for iOS Safari debugging

Logs:
- toggleMenu called with menuOpen state and viewport size
- dropdown element presence check
- computed styles (position, z-index, display, visibility, etc.)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

* fix: override open-upward class in mobile media query

The .open-upward class was setting top: auto and bottom: calc(100% + 4px)
which wasn't being overridden by the mobile media query's .menu-dropdown
styles, causing the dropdown to render at top: -218px (off-screen).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

---------

Co-authored-by: Claude Opus 4.5 <[e-mail]>

frontend/src/lib/components/AddToMenu.svelte

···
 			transform: translateZ(0);
 		}
 
-		.menu-dropdown {
+		.menu-dropdown,
+		.menu-dropdown.open-upward {
 			position: fixed;
 			top: 0;
 			bottom: auto;