Resolve minor JSON:API issues

[edan-bainglass]

This PR refactors and centralizes the handling of JSON:API and JSON
Schema responses throughout the codebase. It introduces new response
classes in a shared module, updates all routers to use these classes,
and moves error handling utilities to a dedicated module. Additionally,
the daemon router endpoints are updated to return plain dictionaries
instead of Pydantic models for status responses.

The PR also fixes a bug in the nodes schema endpoint to ensure the
correct model is selected based on the which parameter.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.77778% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.09%. Comparing base (d17ed6e) to head (fa0fa2d).

Files with missing lines	Patch %	Lines
aiida_restapi/routers/nodes.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
+ Coverage   89.06%   89.09%   +0.02%     
==========================================
  Files          49       50       +1     
  Lines        2030     2035       +5     
==========================================
+ Hits         1808     1813       +5     
  Misses        222      222              

Flag	Coverage Δ
pytests	89.09% <97.77%> (+0.02%)	⬆️

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[Bud-Macaulay]

A lot of small changes to return types, i guess you were having issues with json api.

Happy to approve if it works on your end.

[edan-bainglass]

A lot of small changes to return types, i guess you were having issues with json api.

The return types changes are for consistency. In the original work (#101), I had to change the return type to dict and let it run against the specific response model, instead of returning the model itself, which caused issues due to the abstractness of the JSON:API adapter system. Hence, I found it in general better to return raw dicts and only use Pydantic as a validation gate.