feat(license): add CC BY-ND 4.0 with Standards Integrity Addendum

- Replace CC BY 4.0 with CC BY-ND 4.0 base license
- Add Standards Integrity Addendum (AI laundering, conformance tiers)
- Create JSON Schema v1 at /assets/schema/v1.json
- Add 6 technical conformance tests
- Add W3C-style metadata table to homepage
- Update FAQ to remove "open source" claim

BREAKING CHANGE: License updated to CC BY-ND 4.0 with additional
restrictions on derivative standards and AI-generated content.

Author: marklearst

LICENSE

@@ -68,7 +68,7 @@ include attribution visible to end users:
 B.2 METADATA ATTRIBUTION
 JSON files claiming conformance should include:
 
-    "$schema": "https://variables-contract.vercel.app/schema/v1.json"
+    "$schema": "https://variables-contract.vercel.app/assets/schema/v1.json"
 
 ---