Align milestone charts and self-share flow

src/app/(main)/api/social-milestones/[id]/route.ts

@@ -1,4 +1,4 @@
-import { randomUUID } from 'crypto';
+import { randomBytes } from 'crypto';
 import { NextRequest, NextResponse } from 'next/server';
 import { db } from '@/lib/db';
 import { csrfProtection } from '@/lib/csrf';
@@ -78,7 +78,9 @@ export async function PATCH(request: NextRequest, { params }: { params: { id: st
   const now = new Date();
 
   if (body.action === 'self_share') {
-    const token = milestone.shareToken || randomUUID().replace(/-/g, '');
+    // 72 random bits keep public URLs unguessable while making the share URL
+    // much less disruptive in an X compose window than a full UUID.
+    const token = milestone.shareToken || randomBytes(9).toString('base64url');
     const updated = await db.socialMilestone.update({
       where: { id: milestone.id },
       data: { selfSharedAt: now, publicShareApprovedAt: now, shareToken: token, cardData: card, language },