Add deck generation and study flow improvements

package.json

@@ -6,7 +6,8 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "test": "vitest run"
   },
   "dependencies": {
     "@dnd-kit/core": "^6.3.1",
@@ -23,6 +24,7 @@
     "react-dom": "19.2.4",
     "react-markdown": "^10.1.0",
     "remark-gfm": "^4.0.1",
+    "ts-fsrs": "^5.4.1",
     "zod": "^4.4.3"
   },
   "devDependencies": {
@@ -34,6 +36,7 @@
     "eslint-config-next": "16.2.9",
     "prisma": "^7.8.0",
     "tailwindcss": "^4",
-    "typescript": "^5"
+    "typescript": "^5",
+    "vitest": "^4.1.10"
   }
 }