fix: PHPStan and test strictness improvements

Add bin/ scripts to PHPStan scanFiles, suppress property.onlyWritten for
by-ref test properties, add exhaustive default match arm, use explicit
expects() on mock stubs, fix data provider return type, and simplify
redundant null check in NotificationServiceTest.

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

modules/notifications/tests/Module/Notifications/Service/NotificationServiceTest.php

@@ -275,7 +275,7 @@ class NotificationServiceTest extends TestCase
         $this->notifRepo->expects($this->once())
             ->method('create')
             ->with($this->callback(function (array $data): bool {
-                return !isset($data['dedupe_fingerprint']) || $data['dedupe_fingerprint'] === null;
+                return !isset($data['dedupe_fingerprint']);
             }))
             ->willReturn(56);