perf: KEEP-1257 Reduce scheduler Docker image from 1.85GB to 267MB

[suisuss]

Summary

Reduces the scheduler Docker image size by 85% (1.85GB → 267MB) by using a separate minimal dependency set instead of copying the full node_modules.

Changes

• Added scheduler/package.json with only 6 required dependencies:
  • @aws-sdk/client-sqs
  • @kubernetes/client-node
  • cron-parser
  • drizzle-orm
  • nanoid
  • postgres
• Added scheduler-deps Docker stage that installs only scheduler dependencies
• Updated scheduler stage to use slim deps instead of full node_modules
• Updated GitHub workflow path filters to trigger rebuilds on scheduler/** changes

Test Plan

• Built scheduler image locally: docker build --target scheduler -t keeperhub-scheduler:slim .
• Verified image size: 267MB (down from 1.85GB)
• Tested scheduler scripts run correctly in slim image
• Verified docker-compose compatibility
• Verified Helm values compatibility

Jira

KEEP-1257