refactor: migrate from Biome to oxlint/oxfmt, remove contact form

- Replace Biome with oxlint + oxfmt (OXC toolchain) for linting and formatting
- Add .oxlintrc.json and .oxfmtrc.json configuration files
- Update VS Code settings and devcontainer to use oxc-vscode extension
- Remove contact form, Resend email integration, and related server action/schema
- Remove unused UI components (accordion, alert, card, tabs, toggle, etc.)

components/ui/skeleton.tsx

@@ -4,7 +4,7 @@ function Skeleton({ className, ...props }: React.ComponentProps<"div">) {
   return (
     <div
       data-slot="skeleton"
-      className={cn("animate-pulse rounded-md bg-accent", className)}
+      className={cn("bg-muted animate-pulse rounded-md", className)}
       {...props}
     />
   );