fix: add BASE_URL environment variable for Linkwarden email links

- Add BASE_URL pointing to https://links.pivoine.art
- Required for email verification and password reset links

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

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

links/compose.yaml

@@ -12,6 +12,7 @@ services:
       NEXTAUTH_URL: https://${LINKS_TRAEFIK_HOST}
       MEILI_ADDR: http://linkwarden_meilisearch:7700
       MEILI_MASTER_KEY: ${LINKS_MEILI_MASTER_KEY}
+      BASE_URL: https://${LINKS_TRAEFIK_HOST}
       NEXT_PUBLIC_EMAIL_PROVIDER: true
       EMAIL_FROM: ${EMAIL_FROM}
       EMAIL_SERVER: ${LINKS_EMAIL_SERVER}