Both buttons previously used their default heights (Save inherited 14px
font + button padding; Get-free-key had 6/12 padding + 13px font)
producing a visible height mismatch — Save looked ~5px shorter than
the signup button and sat higher in the row.

Fix: give both `display:inline-flex; align-items:center;
justify-content:center; height:32px; min-width:110px; font-size:13px;
font-weight:600; padding:0 14px`. The input in between also gets
height:32px + box-sizing:border-box so all three (input, Save, signup)
form a clean pixel-aligned row.

Bumps to 0.3.2.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>