chore: add Apache-2.0 SPDX license headers

[tnunamak]

Adds Apache-2.0 SPDX headers to 57 first-party source files.

• Added: Language-appropriate headers with shebangs preserved.
• Skipped: 17 versioned connector scripts because their immutable source hashes require release-version bumps; 19 fixtures/captured files, 21 generated or release outputs, 1 lockfile, plus config, data, and unsupported assets.
• Verified: connector-index, fixture-index, fixture validation, scope-catalog, artifact-contract tests, syntax checks, and git diff --check pass.

[github-actions]

Schema Health Check — All Clear

All 50 scopes have consistent local schema files.