fix(pdf): remove broken helvetica font registration causing 500 error

lib/pdf-page.tsx

@@ -1,14 +1,8 @@
 import * as React from 'react';
 import { Document, Page, View, Text, StyleSheet, Font, Link } from '@react-pdf/renderer';
 
-// Register fonts (using system fonts for now, can be customized)
-Font.register({
-  family: 'Helvetica',
-  fonts: [
-    { src: '/fonts/Helvetica.ttf', fontWeight: 400 },
-    { src: '/fonts/Helvetica-Bold.ttf', fontWeight: 700 },
-  ],
-});
+// Standard fonts like Helvetica are built-in to PDF and don't require registration
+// unless we want to use specific TTF files. Using built-in Helvetica for maximum stability.
 
 // ─── Brand Tokens (matching datasheet) ──────────────────────────────────
 const C = {