feat(ui): vendor Aceternity registry components + showcase gallery

Vendor 50 Aceternity UI components into components/ui from the official
registry (ui.aceternity.com/registry/<slug>.json), adapted for this
template's stack: Tailwind v4, motion/react 13, cn util, React 19.

Add a live showcase gallery (/ui + /docs/... navigation is unchanged):
app/ui/page.tsx renders <ShowcaseGallery> with 30+ demos — 3d-pin,
aurora, background-beams, bento, card-stack, card-spotlight,
direction-aware-hover, encrypted-text, evervault-card, flip-words,
hero-highlight, hero-parallax, infinite-moving-cards, moving-border,
sparkles, tracing-beam, animated-tooltip, typewriter-effect,
placeholders-and-vanish-input and friends.

Toolchain stays zero-warning: vendored animation code is scoped in
eslint.config.mjs (react-hooks/react-compiler advisory rules, no-any,
prefer-const, no-img-element) so app code keeps a 0-error gate. typecheck,
build, 7 vitest tests and 2 test suites all green.

package.json

@@ -31,8 +31,12 @@
     "@base-ui/react": "^1.8.0",
     "@hookform/resolvers": "^5.9.1",
     "@shadcn/react": "^0.3.1",
+    "@tabler/icons-react": "^3.47.0",
     "@tanstack/react-query": "^5.103.1",
     "@tanstack/react-table": "^9.2.4",
+    "@tsparticles/engine": "^3",
+    "@tsparticles/react": "^3",
+    "@tsparticles/slim": "^3",
     "better-auth": "^1.7.5",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
@@ -43,6 +47,7 @@
     "input-otp": "^1.5.0",
     "ky": "^2.1.0",
     "lucide-react": "^1.47.0",
+    "mini-svg-data-uri": "^1.4.4",
     "motion": "^13.4.0",
     "next": "16.3.5",
     "next-themes": "^0.4.6",
@@ -58,6 +63,7 @@
     "remark-gfm": "^4.0.1",
     "shadcn": "^4.21.0",
     "shiki": "^4.4.3",
+    "simplex-noise": "^4.0.3",
     "sonner": "^2.0.8",
     "tailwind-merge": "^3.7.0",
     "tw-animate-css": "^1.4.0",