refactor: migrate to eslint flat config and format codebase with prettier

- Remove legacy .eslintrc.cjs and .eslintignore
- Add eslint.config.js with flat config, security rules (no-eval, no-implied-eval, no-new-func, no-script-url)
- Add .prettierrc and .prettierignore
- Format entire codebase with prettier

src/components/common/PageLoader.tsx

@@ -1,14 +1,16 @@
 interface PageLoaderProps {
-  variant?: 'dark' | 'light'
+  variant?: 'dark' | 'light';
 }
 
 export default function PageLoader({ variant = 'dark' }: PageLoaderProps) {
-  const bgClass = variant === 'dark' ? 'bg-dark-950' : 'bg-gray-50'
-  const spinnerColor = variant === 'dark' ? 'border-accent-500' : 'border-blue-500'
+  const bgClass = variant === 'dark' ? 'bg-dark-950' : 'bg-gray-50';
+  const spinnerColor = variant === 'dark' ? 'border-accent-500' : 'border-blue-500';
 
   return (
-    <div className={`min-h-screen flex items-center justify-center ${bgClass}`}>
-      <div className={`w-10 h-10 border-[3px] ${spinnerColor} border-t-transparent rounded-full animate-spin`} />
+    <div className={`flex min-h-screen items-center justify-center ${bgClass}`}>
+      <div
+        className={`h-10 w-10 border-[3px] ${spinnerColor} animate-spin rounded-full border-t-transparent`}
+      />
     </div>
-  )
+  );
 }