feat: rebrand to Slate (logo, palette, copy, Launch button)

- Wordmark SVG + favicon (#FF1F8F → #00D4FF gradient)
- Page title: Slate — AI App Builder
- Header logo via inline component (no external font deps)
- Deploy button label -> Launch
- Chat placeholder + example prompt rebranded
- Replace upstream accent palette with magenta primary, add cyan2 for accents
- Settings tab notes upstream remains stackblitz-labs/bolt.diy

icons/logo-text.svg

@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 51 21.9"><path d="M24.1 19.3c-4.7 0-7-2.7-7-6.1s3.2-7.7 7.9-7.7 7 2.7 7 6.1-3.2 7.7-7.9 7.7Zm.2-4.3c1.6 0 2.7-1.5 2.7-3.1s-.8-2-2.2-2-2.7 1.5-2.7 3.1.8 2 2.2 2ZM37 19h-4.9l4-18.2H41l-4 18.1Z"/><path d="M9.6 19.3c-1.5 0-3-.5-3.8-1.7L5.5 19 0 21.9.6 19 4.6.8h4.9L8.1 7.2c1.1-1.2 2.2-1.7 3.6-1.7 3 0 4.9 1.9 4.9 5.5s-2.3 8.3-7 8.3Zm1.9-7.3c0 1.7-1.2 3-2.8 3s-1.7-.3-2.2-.9l.8-3.3c.6-.6 1.2-.9 2-.9 1.2 0 2.2.9 2.2 2.2Z" style="fill-rule:evenodd"/><path d="M46.1 19.3c-2.8 0-4.9-1-4.9-3.3s0-.7.1-1l1.1-4.9h-2.2l1-4.2h2.2l.8-3.6L49.7 0l-.6 2.3-.8 3.6H51l-1 4.2h-2.7l-.7 3.2v.6c0 .6.4 1.1 1.2 1.1s.6 0 .7-.1v3.9c-.5.4-1.4.5-2.3.5Z"/></svg>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 70 22"><text x="0" y="18" font-family="Inter, system-ui, -apple-system, Segoe UI, sans-serif" font-weight="700" font-size="20" fill="currentColor" letter-spacing="-0.5">Slate</text></svg>