Add Docker login support

[einichi]

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Description

Allows the use of private docker repositories, such as ghcr.io when used with private repos, by exposing "docker login" to the Dockge UI

Type of change

• User interface (UI)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update (maybe?)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods)
• My changes generate no new warnings

Screenshots (if any)