implement website share functionality using share table

- Add support for multiple share URLs per website with server-generated slugs
- Create shares API endpoint for listing and creating website shares
- Add SharesTable, ShareEditButton, ShareDeleteButton components
- Move share management to website settings, remove header share button
- Remove shareId from website update API (now uses separate share table)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/(main)/websites/[websiteId]/settings/WebsiteSettings.tsx

@@ -1,14 +1,11 @@
 import { Column } from '@umami/react-zen';
 import { Panel } from '@/components/common/Panel';
-import { useWebsite } from '@/components/hooks';
 import { WebsiteData } from './WebsiteData';
 import { WebsiteEditForm } from './WebsiteEditForm';
 import { WebsiteShareForm } from './WebsiteShareForm';
 import { WebsiteTrackingCode } from './WebsiteTrackingCode';
 
 export function WebsiteSettings({ websiteId }: { websiteId: string; openExternal?: boolean }) {
-  const website = useWebsite();
-
   return (
     <Column gap="6">
       <Panel>
@@ -18,7 +15,7 @@ export function WebsiteSettings({ websiteId }: { websiteId: string; openExternal
         <WebsiteTrackingCode websiteId={websiteId} />
       </Panel>
       <Panel>
-        <WebsiteShareForm websiteId={websiteId} shareId={website.shareId} />
+        <WebsiteShareForm websiteId={websiteId} />
       </Panel>
       <Panel>
         <WebsiteData websiteId={websiteId} />