fix: add environment variables and disable health checks for Pastel services

Fixed Pastel color palette generator services in Kit stack:
- Disabled health checks for pastel_api (curl not available in image)
- Disabled health checks for pastel_ui (unnecessary)
- Added NEXT_PUBLIC_API_URL environment variable to pastel_ui
- Added NEXT_PUBLIC_APP_URL environment variable to pastel_ui

Health checks were showing containers as unhealthy even though services
were running correctly. The API health check used curl which isn't
installed in the image, causing false negatives.

Environment variables configure the Next.js frontend to correctly
connect to the API endpoint.

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

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

kit/compose.yaml

@@ -85,6 +85,8 @@ services:
     image: ${KIT_PASTEL_API_IMAGE:-ghcr.io/valknarness/pastel-api:latest}
     container_name: ${KIT_COMPOSE_PROJECT_NAME}_pastel_api
     restart: unless-stopped
+    healthcheck:
+      disable: true
     networks:
       - compose_network
     labels:
@@ -110,6 +112,11 @@ services:
     image: ${KIT_PASTEL_UI_IMAGE:-ghcr.io/valknarness/pastel-ui:latest}
     container_name: ${KIT_COMPOSE_PROJECT_NAME}_pastel_ui
     restart: unless-stopped
+    healthcheck:
+      disable: true
+    environment:
+      - NEXT_PUBLIC_API_URL=https://${KIT_PASTEL_TRAEFIK_HOST}
+      - NEXT_PUBLIC_APP_URL=https://${KIT_PASTEL_TRAEFIK_HOST}
     networks:
       - compose_network
     labels: