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/dialog.tsx

@@ -48,7 +48,7 @@ const DialogContent = React.forwardRef<
         // Long forms get an internal scroll cap so the close button + footer
         // stay reachable without scrolling the whole page.
         'fixed top-0 right-0 bottom-0 left-0 z-50 grid w-full gap-4 border-0 bg-background p-4 shadow-lg duration-200 sm:p-6',
-        'max-h-[100dvh] overflow-y-auto sm:max-h-[calc(100dvh-2rem)]',
+        'max-h-dvh overflow-y-auto sm:max-h-[calc(100dvh-2rem)]',
         'data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0',
         'sm:top-[50%] sm:right-auto sm:bottom-auto sm:left-[50%] sm:max-w-lg sm:translate-x-[-50%] sm:translate-y-[-50%] sm:border sm:rounded-lg',
         'sm:data-[state=closed]:zoom-out-95 sm:data-[state=open]:zoom-in-95 sm:data-[state=closed]:slide-out-to-left-1/2 sm:data-[state=closed]:slide-out-to-top-[48%] sm:data-[state=open]:slide-in-from-left-1/2 sm:data-[state=open]:slide-in-from-top-[48%]',
@@ -57,7 +57,7 @@ const DialogContent = React.forwardRef<
       {...props}
     >
       {children}
-      <DialogPrimitive.Close className="absolute right-4 top-4 rounded-sm opacity-70 ring-offset-background transition-opacity hover:opacity-100 focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none data-[state=open]:bg-accent data-[state=open]:text-muted-foreground">
+      <DialogPrimitive.Close className="absolute right-4 top-4 rounded-sm opacity-70 ring-offset-background transition-opacity hover:opacity-100 focus:outline-hidden focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none data-[state=open]:bg-accent data-[state=open]:text-muted-foreground">
         <X className="h-4 w-4" />
         <span className="sr-only">Close</span>
       </DialogPrimitive.Close>