test(auth): add 68 unit tests for auth-ui, shared-auth, and shared-branding

- userAgent utils: parseUserAgent, getDeviceType, formatUserAgent (17 tests)
- guestWelcome utils: shouldShow, markSeen, reset (8 tests)
- jwtUtils: decodeToken, isTokenValid, getUserFromToken, B2B (27 tests)
- mana-apps: hasAppAccess, getTierLevel, getAccessibleManaApps (16 tests)

Also fixes iOS detection bug in userAgent parser (iPhone UA contains
"Mac OS X" — mobile check must come before desktop OS check).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-auth/package.json

@@ -12,6 +12,8 @@
 	"scripts": {
 		"build": "tsc",
 		"clean": "rm -rf dist",
+		"test": "vitest run",
+		"test:watch": "vitest",
 		"type-check": "tsc --noEmit",
 		"lint": "eslint ."
 	},