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

app/components/header/HeaderActionButtons.client.tsx

@@ -77,7 +77,7 @@ export function HeaderActionButtons({}: HeaderActionButtonsProps) {
             onClick={() => setIsDropdownOpen(!isDropdownOpen)}
             className="px-4 hover:bg-bolt-elements-item-backgroundActive flex items-center gap-2"
           >
-            {isDeploying ? `Deploying to ${deployingTo}...` : 'Deploy'}
+            {isDeploying ? `Launching to ${deployingTo}...` : 'Launch'}
             <div
               className={classNames('i-ph:caret-down w-4 h-4 transition-transform', isDropdownOpen ? 'rotate-180' : '')}
             />