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/api/share/route.ts

@@ -1,5 +1,6 @@
 import z from 'zod';
 import { uuid } from '@/lib/crypto';
+import { getRandomChars } from '@/lib/generate';
 import { parseRequest } from '@/lib/request';
 import { json, unauthorized } from '@/lib/response';
 import { anyObjectParam } from '@/lib/schema';
@@ -10,7 +11,7 @@ export async function POST(request: Request) {
   const schema = z.object({
     entityId: z.uuid(),
     shareType: z.coerce.number().int(),
-    slug: z.string().max(100),
+    slug: z.string().max(100).optional(),
     parameters: anyObjectParam,
   });
 
@@ -30,7 +31,7 @@ export async function POST(request: Request) {
     id: uuid(),
     entityId,
     shareType,
-    slug,
+    slug: slug || getRandomChars(16),
     parameters,
   });