#274 CONV-313: Create OpenAPI specification skeleton

Summary

• Creates docs/api/openapi.yaml with OpenAPI 3.1.0 skeleton
• Adds Bearer API key security scheme
• Adds /api/v1 server URLs (production + local)
• Adds tests/Feature/Docs/OpenApiSpecificationTest.php

Test plan

• Test written first (TDD) — fails before implementation
• composer test passes (602 tests)

🤖 Generated with Claude Code

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Summary by cubic

Add an OpenAPI 3.1.0 skeleton for the File Converter API to establish a baseline spec and align with CONV-313. Includes Bearer API key auth and /api/v1 server URLs; adds a basic test that asserts docs/api/openapi.yaml exists.