feat: add clear-cache job

[krupanshi-itpl]

Description

When upgrading the Frappe/ERPNext Docker image via the Helm chart, the application may continue to serve stale frontend assets (JS/CSS) or cached data. This can result in UI breakages, mismatched assets, or unexpected behavior even though the new image is running successfully.

This PR adds an optional cache-clearing Job, implemented as a post-upgrade Helm hook, that runs after an upgrade to ensure cache consistency.

Keypoints

• The Job is disabled by default
• Cleans up automatically after successful execution
• An initContainer is available to wait for the ERPNext deployment rollout which is disabled by default to avoid additional upgrade delayes. Can be enabled explicitly if required.

Job responsibilites

1. Clear website cache:
   bench --site all clear-website-cache
2. Clear application cache:
   bench --site all clear-cache
3. Optionally flush Redis cache:
   bench --site all execute "frappe.cache.flushdb"

Configuration

Example of values.yaml:

jobs:
  clearCache:
    enabled: true
    initContainer:
      enabled: false
    redisFlush:
      enabled: true

Backward Compatibility

• Disabled by default
• No behavior changes unless explicitly enabled

Fixes

Closes #274

[revant]

I did that with annotation change in values:

redis-cache:
  image:
    registry: docker.io
    repository: bitnamilegacy/redis
  master:
    podAnnotations:
      deployed-at: "2025-12-03 18:00:00"