The duplicate functions at lines 455-486 were redefining cacheElements and
bindEvents with wrong element IDs (kebab-case vs camelCase in HTML).
This caused 'Cannot read properties of null' error on slides app init.
- Changed apps-dropdown right position from 60px to 0 in app.css
- Wrapped apps button and dropdown in a container with position:relative
- Moved dropdown to be a sibling of the button inside the container
- Removed duplicate dropdown from header-right section
