fix: use URL-encoded EMAIL_SERVER variable for Linkwarden

- Use dedicated LINKS_EMAIL_SERVER variable with proper URL encoding
- Encode @ symbol in email address as %40 to avoid URL parsing conflicts
- Fixes NextAuth error: "Cannot read properties of undefined (reading 'split')"

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

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

links/compose.yaml

@@ -14,7 +14,7 @@ services:
       MEILI_MASTER_KEY: ${LINKS_MEILI_MASTER_KEY}
       NEXT_PUBLIC_EMAIL_PROVIDER: true
       EMAIL_FROM: ${EMAIL_FROM}
-      EMAIL_SERVER: smtps://${EMAIL_SMTP_USER}:${EMAIL_SMTP_PASSWORD}@${EMAIL_SMTP_HOST}:${EMAIL_SMTP_PORT}
+      EMAIL_SERVER: ${LINKS_EMAIL_SERVER}
     volumes:
       - linkwarden_data:/data/data
     depends_on: