fix: helm-install task to use channel slug instead of channel ID for helmfile sync

- Add utility functions for channel ID/slug conversion (get-channel-slug, get-channel-id)
- Fix customer-helm-install to convert channel ID to channel slug before calling helmfile
- Fix customer-full-test-cycle channel ID lookup (.channelId → .id)
- Replace inline name normalization with centralized utils:normalize-name function
- Consolidate all name normalization logic for consistent git branch handling

This resolves OCI repository format errors where helmfile expected channel slugs
but was receiving channel IDs, causing invalid registry URLs like:
registry.replicated.com/app/CHANNEL_ID/chart vs registry.replicated.com/app/channel-slug/chart

Author: adamancini