feat: add Vaultwarden Docker setup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+  vaultwarden:
+    image: vaultwarden/server:latest
+    container_name: vaultwarden
+    restart: always
+    volumes:
+      - ./data:/data
+    ports:
+      - "8080:80"
+    environment:
+      WEBAUTHN_ENABLED: "true"
+      WEBSOCKET_ENABLED: "true"
+      ADMIN_TOKEN: ${VAULTWARDEN_ADMIN_TOKEN}
+