feat(testing): Auth.fake(), Cache.fake(), Vault.fake(), Log.fake() — facade faking ecosystem (#19) (#23)

Add Laravel-style fake()/unfake() to Auth, Cache, Vault, Log facades
following the Http.fake() pattern from #18. Each fake replaces the
IoC-bound service with an in-memory test double that records operations
and supports assertion methods — no mockito needed.

- FakeAuthManager with internal FakeGuard (login/logout/check/user)
- FakeCacheManager with in-memory CacheStore (get/put/has/forget/flush)
- FakeVaultService with in-memory secure storage (no FlutterSecureStorage)
- FakeLogManager with silent log capture (all RFC 5424 levels)
- Auth facade refactored from direct singleton to IoC resolution
- AuthManager.forTesting() + MagicVaultService.forTesting() constructors
- 130 new tests, 649 total passing

Author: anilcancakir

CHANGELOG.md

@@ -6,6 +6,7 @@ All notable changes to this project will be documented in this file.
 
 ### ✨ Features
 - **Http Faking**: `Http.fake()` enables Laravel-style HTTP faking for testing. Swap the real network driver with a `FakeNetworkDriver` that records requests and returns stubbed responses. Supports URL pattern stubs, callback stubs, and assertion methods (`assertSent`, `assertNotSent`, `assertNothingSent`, `assertSentCount`). (#18)
+- **Facade Faking**: `Auth.fake()`, `Cache.fake()`, `Vault.fake()`, `Log.fake()` — Laravel-style facade faking for testing. Swap real service implementations with in-memory fakes that record operations and expose assertion helpers. (#19)
 
 ## [1.0.0-alpha.5] - 2026-03-29