feat: add email verification check to unsubscribe page

Security Enhancement:
- Server-side validation of email status before allowing unsubscribe
- Only allow unsubscribing from verified emails
- Show "Action Not Allowed" message for unverified/unsubscribed emails
- Extract and validate share-id on server side
- Return 404 for invalid share-ids or missing tenant emails

Implementation:
- Convert page.tsx to async server component
- Fetch location and check tenantEmailStatus
- Pass isVerified prop to client component
- Add bilingual "not-allowed" translations

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

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

web-app/messages/en.json

@@ -482,6 +482,10 @@
     "error": {
       "title": "Unsubscribe Failed",
       "unknown": "An error occurred while unsubscribing. Please try again or contact your landlord."
+    },
+    "not-allowed": {
+      "title": "Action Not Allowed",
+      "message": "You can only unsubscribe from verified email addresses. This email address has not been verified yet or has already been unsubscribed."
     }
   },
   "privacy-policy-page": {