Add @shlinkio/dashboard-server local package in src folder

[acelaya]

Closes #589

In order to be able to use all server domain code in production, for the react-router app, but also other entry points, this PR extracts that to its own meta-package, that is marked as external for vite and bundled individually.

That way, react-router's server bundle does not include that code, but instead just consume it as another external dependency.

Other entry points can do the same.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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  Hits               ?     1783           
  Misses             ?      301           
  Partials           ?      393           

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