build(frontend): upgrade to tailwindcss v4

- Upgrade to Tailwind CSS v4.2.0 with explicit CLI dependency
- Add @tailwindcss/cli and tailwindcss as devDependencies
- Update build scripts to use bunx @tailwindcss/cli
- Include new transitive dependencies for enhanced CSS processing

frontend/package.json

@@ -2,17 +2,19 @@
   "name": "aethera",
   "private": true,
   "scripts": {
-    "dev": "bun build src/main.ts --outdir public/dist --target browser --watch & tailwindcss -i styles.css -o public/dist/styles.css --watch",
-    "build": "bun build src/main.ts --outdir public/dist --target browser && tailwindcss -i styles.css -o public/dist/styles.css --minify",
+    "dev": "bun build src/main.ts --outdir public/dist --target browser --watch & bunx @tailwindcss/cli -i styles.css -o public/dist/styles.css --watch",
+    "build": "bun build src/main.ts --outdir public/dist --target browser && bunx @tailwindcss/cli -i styles.css -o public/dist/styles.css --minify",
     "lint": "eslint ./src/**"
   },
   "devDependencies": {
+    "@tailwindcss/cli": "^4.1.18",
     "@tailwindcss/typography": "^0.5.19",
     "@types/alpinejs": "^3.13.11",
     "@types/bun": "latest",
     "@typescript-eslint/eslint-plugin": "^8.52.0",
     "@typescript-eslint/parser": "^8.52.0",
-    "eslint": "^9.39.2"
+    "eslint": "^9.39.2",
+    "tailwindcss": "^4.1.18"
   },
   "peerDependencies": {
     "typescript": "^5"