feat: Add customizable liveness probe settings

[lexfrei]

Description

Add ability to customize liveness probe parameters, particularly failureThreshold.

Why is this needed?

The current hardcoded failureThreshold: 1 can be too aggressive in some environments. Users should be able to configure:

• failureThreshold
• timeoutSeconds
• periodSeconds
• initialDelaySeconds

Implementation details

• Add livenessProbe section in values.yaml with sensible defaults
• Update deployment template to use configurable values
• Maintain backward compatibility
• Add corresponding tests

Reference

• Upstream PR: Add support for customizable livenessProbe.failureThreshold cloudflare/helm-charts#82

Acceptance Criteria

• Configurable liveness probe parameters
• Values.yaml updated with probe settings
• Tests added
• Documentation updated

[lexfrei]

Closing in favor of grouped issues for better project management