feat(api): expose organism associations on molecules REST resource

[vcnainala]

Summary

• Add organisms as an includable BelongsToMany relation on MoleculeResource, reusing the existing OrganismResource fields (name, iri, rank, molecule_count).
• Expose organism_count on molecule records so clients can show counts without eager-loading the full relation.
• Document the new include in docs/api-documentation.md and regenerate public/vendor/rest/openapi.json.

Test plan

• Authenticate and POST /api/molecules/search with includes: [{ "relation": "organisms" }] for a known molecule identifier
• Verify response includes nested organisms with name, iri, rank, molecule_count
• Verify organism_count is filterable/sortable in molecule search
• Confirm OpenAPI spec lists organisms under molecule relations

Resolves

Closes #781

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 6.09%. Comparing base (a4c26c6) to head (f9010ca).
⚠️ Report is 4 commits behind head on development.

Files with missing lines	Patch %	Lines
app/Rest/Resources/MoleculeResource.php	0.00%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##             development    #794      +/-   ##
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- Coverage           6.14%   6.09%   -0.06%     
- Complexity          1736    1737       +1     
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  Files                227     227              
  Lines               8945    8963      +18     
================================================
- Hits                 550     546       -4     
- Misses              8395    8417      +22     

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