fix: preserve saved seed on page reload

The bug: Server-side page.tsx was ALWAYS generating a new seed with
Date.now() on every page load, even when loading saved settings from
the database. This caused different problems on every reload.

The fix:
- Check if saved config has a seed, use it if present
- Only generate new seed if no saved seed exists (first visit)
- Also preserve prngAlgorithm from saved config

This ensures:
- Reloading the page shows the same problems (from auto-saved seed)
- Shared worksheets show same problems (from shared seed)
- First-time visitors get a new random seed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/app/create/worksheets/page.tsx

@@ -41,25 +41,31 @@ async function loadWorksheetSettings(): Promise<
       .limit(1)
 
     if (!row) {
-      // No saved settings, return defaults with a stable seed
+      // No saved settings, return defaults with a new seed
       return {
         ...defaultAdditionConfig,
         seed: Date.now() % 2147483647,
+        prngAlgorithm: 'mulberry32',
       } as unknown as Omit<WorksheetFormState, 'date' | 'rows' | 'total'>
     }
 
     // Parse and validate config (auto-migrates to latest version)
     const config = parseAdditionConfig(row.config)
+
+    // CRITICAL: Use saved seed if present, otherwise generate new one
+    // This ensures reloading the page shows the same problems
     return {
       ...config,
-      seed: Date.now() % 2147483647,
+      seed: (config as any).seed ?? Date.now() % 2147483647,
+      prngAlgorithm: (config as any).prngAlgorithm ?? 'mulberry32',
     } as unknown as Omit<WorksheetFormState, 'date' | 'rows' | 'total'>
   } catch (error) {
     console.error('Failed to load worksheet settings:', error)
-    // Return defaults on error with a stable seed
+    // Return defaults on error with a new seed
     return {
       ...defaultAdditionConfig,
       seed: Date.now() % 2147483647,
+      prngAlgorithm: 'mulberry32',
     } as unknown as Omit<WorksheetFormState, 'date' | 'rows' | 'total'>
   }
 }