Add @dfx.swiss/core package

[TaprootFreak]

Summary

• New @dfx.swiss/core package: framework-agnostic API client and TypeScript type definitions
• Extracted all 24 type definition files from @dfx.swiss/react (zero React dependency)
• DfxApiClient class with typed methods for all DFX API endpoints (auth, buy, sell, swap, asset, fiat, country, user, kyc, transaction, support, payment links/routes, settings, bank accounts)
• Zero external dependencies — only requires a global fetch function
• Added monorepo tsconfig path alias for @dfx.swiss/core

Motivation

Currently, any non-React consumer (Edge Wallet, CLI tools, React Native apps, Node.js backends) must reimplement DFX API types and HTTP calls from scratch. This package provides a single source of truth for the DFX API contract.

Usage

import { DfxApiClient, Blockchain } from '@dfx.swiss/core';

const client = new DfxApiClient({ apiUrl: 'https://api.dfx.swiss/v1' });
const assets = await client.asset.list({ blockchains: [Blockchain.BITCOIN] });

const msg = await client.auth.getSignMessage(address);
const { accessToken } = await client.auth.authenticate({ address, signature, wallet: 'edge' });
client.setToken(accessToken);

const quote = await client.buy.quote({ currency, asset, amount: 100 });

Follow-ups

• Refactor @dfx.swiss/react to consume types/client from core
• Move Utils and Validations to core (currently still in react)
• Migrate Edge Wallet plugin to use @dfx.swiss/core

Test plan

• tsc build succeeds with zero errors
• All 24 definition files match current @dfx.swiss/react types (synced with latest develop)
• Review API method signatures against actual DFX API
• Integration test with Edge Wallet plugin