feat: add issueJwt() for server-side authentication

[tysonwil]

Summary

• Adds issueJwt(keyIndex:) method to ParaManager for server-side authentication
• Returns JwtResponse containing the signed token and key ID
• JWT can be verified using Para's JWKS endpoint at /.well-known/jwks.json

Usage

// After user is authenticated
let jwt = try await para.issueJwt()

// Send to your server
request.setValue("Bearer \(jwt.token)", forHTTPHeaderField: "Authorization")

Server-side verification

import jose from 'jose';

const JWKS = jose.createRemoteJWKSet(
  new URL('https://api.getpara.com/.well-known/jwks.json')
);

const { payload } = await jose.jwtVerify(token, JWKS, {
  audience: 'YOUR_PARA_API_KEY'
});
// payload.sub = userId
// payload.data.wallets = user's wallets

Test plan

• Build succeeds
• Call issueJwt() after authentication and verify JWT is returned
• Decode JWT and verify payload contains expected fields

🤖 Generated with Claude Code