feat: Phase 4 - CI/CD, Static Analysis, Browser Tests

- Add GitHub Actions CI workflow (.github/workflows/ci.yml)
  - Laravel Pint code style check
  - PHPStan static analysis (level 5)
  - Test suite with parallel execution
  - Dusk browser tests (disabled by default)
- Add phpstan.neon config (level 5, ignores User notifications methods)
- Add Dusk browser tests (ProjectWorkflowTest)
- Install laravel/dusk + chromedriver

Tests: 101 passing (319 assertions)

phpstan.neon

@@ -0,0 +1,8 @@
+parameters:
+    level: 5
+    paths:
+        - app
+        - routes
+    ignoreErrors:
+        - '#Undefined method .*::notifications\(\)#'
+        - '#Undefined method .*::unreadNotifications\(\)#'