add Touch ID wallet unlock via Swift biometric helper + Bun spawn

apps/desktop/src/bun/lib/biometric.ts

@@ -0,0 +1,31 @@
+import { existsSync } from 'fs'
+import { join } from 'path'
+import { fileURLToPath } from 'url'
+import { PATHS } from 'electrobun/bun'
+
+const __dirname = fileURLToPath(new URL('.', import.meta.url))
+
+function findHelper(): string {
+	const candidates = [
+		join(__dirname, '..', 'native', 'biometric-helper'),
+		join(PATHS.RESOURCES_FOLDER, 'native', 'biometric-helper'),
+	]
+	for (const p of candidates) {
+		if (existsSync(p)) return p
+	}
+	throw new Error(
+		`biometric-helper not found at any of:\n${candidates.join('\n')}`,
+	)
+}
+
+const HELPER_PATH = findHelper()
+
+export function canPromptTouchID(): boolean {
+	const result = Bun.spawnSync([HELPER_PATH, '--check'])
+	return result.exitCode === 0
+}
+
+export function promptTouchID(reason: string): boolean {
+	const result = Bun.spawnSync([HELPER_PATH, reason])
+	return result.exitCode === 0
+}