🐛 ARIA-TODOs: Fix remaining accessibility issues listed

[KemingHe]

Side Drawer

• Side drawer auto-opens on lg (Tailwind) viewport, must also update isSideDrawerOpen state (?)
• Consider adding an isLargeViewport state/hook in ChatLayoutContext.tsx.
• For < lg viewports (no auto-open), rest of page should be aria-hidden="true".
• For >= lg viewports, rest of page should still be accessible (responsive ARIA).

Sign In

• ARIA hide the @osu.edu on sign in card to avoid confusion.