Add Native Console Proof Providers for Android

[ebariaux]

Add native proof providers so mobile consoles can prove possession of the installed app/device state without exposing reusable secrets to web content.

Provider behavior:

• Add a consoleProof provider to both native console implementations.

• Generate an asymmetric key pair on device.

• Store the private key as non-exportable where possible: Android Keystore

• Expose provider actions to web content:

  • initialize / report provider availability
  • create or load key
  • return public key as JWK
  • sign a challenge payload
  • optionally delete key for “forget this device”

• Do not expose the private key or raw secret to JavaScript.

• Include provider version and supported algorithms, initially ES256 unless implementation constraints require otherwise.

Acceptance criteria:

• Android can generate and persist a key across app restarts.
• Public key can be returned to web content.
• Challenge payload can be signed by native code.
• Private key cannot be read by web content.
• Existing older native shells continue to fall back to Web Crypto/localStorage behavior until updated.