chore(license): align repository compliance text

[johntmyers]

Summary

Align the repository's Apache 2.0 and DCO materials with NVIDIA open-source policy, correct missing or malformed SPDX attribution, and close gaps in the license-header checker.

Related Issue

No issue required: this is a mechanical license-compliance correction with no product behavior change.

Changes

• Add the NVIDIA copyright notice and restore the standard Apache 2.0 appendix in LICENSE
• Include the full Developer Certificate of Origin 1.1 text in CONTRIBUTING.md
• Correct malformed SPDX copyright lines and add headers to the affected deployment, script, Helm, and SDK files
• Add REUSE-compatible .license sidecars for strict JSON files that cannot contain comments
• Extend the license-header checker to validate the complete NVIDIA SPDX header and cover previously skipped source formats

Testing

• mise run pre-commit passes
• mise run helm:test passes (153 tests)
• Shell, JavaScript, and JSON syntax validation passes
• E2E tests added/updated (not applicable; no runtime behavior changed)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable; no architecture changed)