Initial transfer API rail: client, router, docs fetcher, tests

Co-authored-by: Cursor <cursoragent@cursor.com>

jest.config.js

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+/** @type {import('ts-jest').JestConfigWithTsJest} */
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  roots: ['<rootDir>/src'],
+  testMatch: ['**/*.test.ts'],
+  collectCoverageFrom: ['src/**/*.ts', '!src/**/*.test.ts'],
+  coverageDirectory: 'coverage',
+  moduleFileExtensions: ['ts', 'js', 'json'],
+};