feat(deps): Tailwind 3 → 4 + swap tailwindcss-animate for tw-animate-css

Ran the official @tailwindcss/upgrade tool:
- tailwind.config.ts → @theme directive in globals.css
- @tailwind base/components/utilities → @import 'tailwindcss'
- postcss.config switched from tailwindcss + autoprefixer to
  @tailwindcss/postcss (autoprefixer baked in)
- focus-visible:outline-none → focus-visible:outline-hidden (the v3
  utility was a footgun — outline still showed in forced-colors mode)

Reverted the migration tool's over-zealous variant="outline" →
variant="outline-solid" rename on CVA prop values; that rename was
meant for the Tailwind `outline:` utility, not our Button/Badge
component variants.

Swapped tailwindcss-animate (v3-style JS plugin) for tw-animate-css
(v4-native @import). Same utility surface (animate-spin, animate-in,
etc.), one fewer JS plugin in the bundle.

Fixed the upgrade tool's malformed dark variant
(@custom-variant dark (&:is(class *)) — `class` was being parsed as
a tag) to canonical &:where(.dark, .dark *).

Verified: tsc 0 errors, eslint 0 errors (16 pre-existing warnings),
vitest 1315/1315, next build clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/ui/table.tsx

@@ -37,7 +37,7 @@ const TableFooter = React.forwardRef<
 >(({ className, ...props }, ref) => (
   <tfoot
     ref={ref}
-    className={cn('border-t bg-muted/50 font-medium [&>tr]:last:border-b-0', className)}
+    className={cn('border-t bg-muted/50 font-medium last:[&>tr]:border-b-0', className)}
     {...props}
   />
 ));
@@ -64,7 +64,7 @@ const TableHead = React.forwardRef<
   <th
     ref={ref}
     className={cn(
-      'h-10 px-2 text-left align-middle font-medium text-muted-foreground [&:has([role=checkbox])]:pr-0 [&>[role=checkbox]]:translate-y-[2px]',
+      'h-10 px-2 text-left align-middle font-medium text-muted-foreground has-[[role=checkbox]]:pr-0 *:[[role=checkbox]]:translate-y-[2px]',
       className,
     )}
     {...props}
@@ -79,7 +79,7 @@ const TableCell = React.forwardRef<
   <td
     ref={ref}
     className={cn(
-      'p-2 align-middle [&:has([role=checkbox])]:pr-0 [&>[role=checkbox]]:translate-y-[2px]',
+      'p-2 align-middle has-[[role=checkbox]]:pr-0 *:[[role=checkbox]]:translate-y-[2px]',
       className,
     )}
     {...props}