fix: Require value in EnvVarRequest and allow null error messages in request dicts

[apify-service-account]

• Regenerates the Pydantic models, TypedDicts, and literal aliases from the published OpenAPI specification, and records its version in pyproject.toml.
• Specification version: v2-2026-07-28T083939Z -> v2-2026-08-05T133145Z.

Important

Retitle this pull request to fix: or feat: when the diff is user-facing, so that it lands in the changelog and triggers a release - chore: does neither.

Generated by the Regenerate models workflow.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.73%. Comparing base (a6ca0cb) to head (8c20dbc).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/apify_client/_typeddicts.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1001      +/-   ##
==========================================
+ Coverage   94.71%   94.73%   +0.02%     
==========================================
  Files          58       58              
  Lines        5337     5339       +2     
==========================================
+ Hits         5055     5058       +3     
+ Misses        282      281       -1     

Flag	Coverage Δ
integration	92.35% <50.00%> (+0.17%)	⬆️
unit	84.47% <50.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.