improve auth input contrast and autofill styling

[saurabhhhcodes]

What changed

• Made the login password visibility toggle a clearer, visible control with its own contrast, padding, and focus ring.
• Added an auth input autofill style hook to keep the register email field aligned with the dark theme when the browser fills it.

Why

• The login eye icon was too faint to notice reliably.
• Browser autofill was painting the register email field white, breaking the visual theme.

Validation

• git diff --check
• npm run build
• Browser runtime check confirmed the login toggle renders as a 32px control and the register email field carries the autofill class hook.

Closes #211
Closes #205

[vercel]

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