docs(docker): use latest image tag in examples

[qin-ctx]

Description

Update Docker examples and deployment docs to use ghcr.io/volcengine/openviking:latest instead of the stale :main tag.

Related Issue

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Replace ghcr.io/volcengine/openviking:main with :latest in the root docker-compose.yml
• Update English quickstart and deployment guides to match the currently published image tag
• Update Chinese quickstart, deployment, and cloud guides with the same image tag change

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes

No runtime code changed. This PR only updates image tag references in docs and examples.

[github-actions]

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