[TASK] Fix flush-all endpoint missing side effects

Description

Modify the existing DELETE /v1/caches/provider/{provider}/flush endpoint in CacheResource.java to add missing side effects. Currently it only calls MaintenanceUtil.flushCache() but the JSP Struts action also resets permission references and reloads PushPublishing filters after flushing all caches.

Acceptance Criteria

• After calling MaintenanceUtil.flushCache(), endpoint must also call APILocator.getPermissionAPI().resetAllPermissionReferences()
• After calling MaintenanceUtil.flushCache(), endpoint must also call DotInitializer.class.cast(APILocator.getPublisherAPI()).init() to reload PushPublishing filters
• Existing behavior (flushing all caches) must not change
• Existing response format must not change

Priority

None

Additional Context

• Current implementation: CacheResource.java line 338, flushAll() method
• Only consumer is a Postman test collection — no breaking change risk
• The Struts action (ViewCMSMaintenanceAction._flush()) always calls resetAllPermissionReferences() and conditionally reloads PushPublishing filters — the REST endpoint was missing both

Start in CacheResource.java at line 338, in the flushAll() method, and compare its behavior with ViewCMSMaintenanceAction._flush(). Verify the existing Postman test collection for the DELETE /v1/caches/provider/{provider}/flush endpoint, then confirm the permission references and PushPublishing filters are reloaded after cache flushing without changing the response format.