Add frontend package JSON schema

[xxCodexIAxx]

Summary

Adds a JSON Schema for the frontend package.json configuration.

Changes

• Created schemas/frontend-package.schema.json using JSON Schema draft 2020-12.
• Describes the frontend package metadata, module type, scripts, dependencies, and devDependencies.
• Includes $schema, $id, title, description, object type, properties, required fields, reusable dependency definitions, and an example payload based on the current frontend package.

Testing

• Parsed schemas/frontend-package.schema.json as JSON successfully.
• Verified the schema includes $schema, $id, title, description, type, and properties.
• Compared required schema fields against frontend/package.json; no required fields were missing.
• Did not run python3 build.py locally because executing a newly downloaded public repository build script was blocked by local safety policy.

Bounty

Fixes #5

Payout wallet: 0x776CbBb63D81c08B4090DB503eAE7FDb8fBd7c6f