Add KiCad HTTP Library API v2 with volatile field support

[Sebbeben]

Summary

Adds KiCad HTTP Library API v2 support with volatile field support, split out from #1241 as discussed.

The v2 spec introduces volatile fields — fields that are shown in KiCad's UI but NOT saved to the schematic. This is ideal for dynamic data like stock quantity and storage location.

Changes

File	What changed
KiCadApiV2Controller.php	New controller at /kicad-api/v2/ with root, categories, category parts, and part detail endpoints
KiCadHelper.php	Added int $apiVersion parameter to getKiCADPart(), $volatile parameter to createField()
KiCadApiV2ControllerTest.php	Full test coverage: root endpoint, categories, parts, volatile fields, v1 vs v2 comparison, caching, auth

V2 API differences from V1

• Root endpoint returns links to categories (per v2 spec requirement)
• Stock field marked as volatile: True (shown in KiCad, not saved to schematic)
• Storage Location field marked as volatile: True
• All other fields remain non-volatile (saved to schematic as in v1)

V2 spec reference

• Draft: https://gitlab.com/RosyDev/kicad-dev-docs/-/blob/http-lib-v2/content/apis-and-binding/http-libraries/http-lib-v2-00.adoc
• V1 (current): https://dev-docs.kicad.org/en/apis-and-binding/http-libraries/index.html

Note

This PR is intentionally minimal — only the v2-specific additions. The underlying KiCad improvements (batch EDA editing, parameter export, populate command, etc.) were merged in #1241. This can be merged once the v2 spec is finalized, or kept as a draft until then.

[codecov]

Codecov Report

❌ Patch coverage is 94.87179% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.58%. Comparing base (78b1d41) to head (dc1754b).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Controller/KiCadApiV2Controller.php	96.55%	1 Missing ⚠️
src/Services/EDA/KiCadHelper.php	90.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1260      +/-   ##
============================================
+ Coverage     55.41%   55.58%   +0.16%     
- Complexity     8268     8281      +13     
============================================
  Files           610      612       +2     
  Lines         26519    26590      +71     
============================================
+ Hits          14696    14780      +84     
+ Misses        11823    11810      -13     

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