feat: add Linkwarden bookmark manager stack

Added new Links stack to Falcon infrastructure:

**Links Stack (links.pivoine.art):**
- Linkwarden bookmark manager with PostgreSQL backend
- Meilisearch v1.12.8 for full-text search
- Browser extension support
- Screenshot and PDF archiving
- Collaborative bookmark sharing

**Infrastructure Updates:**
- Created links/compose.yaml with linkwarden and meilisearch services
- Added linkwarden database to PostgreSQL init script
- Added LINKS_* environment variables to arty.yml
- Updated compose.yaml to include links stack
- Cleaned up .env to contain only secrets
- Added all EMAIL_* variables to .env

**Documentation:**
- Updated CLAUDE.md with Links service details
- Updated README.md with Links in CORE SYSTEMS table
- Added linkwarden_data and meili_data volumes to docs

**Required Secrets (in .env):**
- LINKS_NEXTAUTH_SECRET: NextAuth.js session encryption
- LINKS_MEILI_MASTER_KEY: Meilisearch API authentication

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

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

arty.yml

@@ -79,6 +79,14 @@ envs:
     STASH_TRAEFIK_HOST: stash.pivoine.art
     STASH_PORT: 8334
     STASH_CANARY: true
+    # Linkwarden
+    LINKS_TRAEFIK_ENABLED: true
+    LINKS_COMPOSE_PROJECT_NAME: links
+    LINKS_DOCKER_IMAGE: ghcr.io/linkwarden/linkwarden:latest
+    LINKS_TRAEFIK_HOST: links.pivoine.art
+    LINKS_DB_NAME: linkwarden
+    LINKS_MEILI_IMAGE: getmeili/meilisearch:v1.12.8
+    LINKS_MEILI_NO_ANALYTICS: true
     # Proxy
     PROXY_COMPOSE_PROJECT_NAME: proxy
     PROXY_DOCKER_IMAGE: traefik:latest