feat: add extensible FrontBlocks settings tabs

[davidperezgar]

Summary

• add a filter for companion plugins to register FrontBlocks settings tabs
• add an action for rendering companion plugin tab panels outside the settings form

Validation

• composer validate --strict
• composer lint
• composer phpstan
• composer test (388 tests, 766 assertions)
• git diff --check

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-03T10:52:56.405087Z	7df3f1f	New commits

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: fc69611e90

ℹ️ About Codex in GitHub

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