## Description
This PR sets up an `Enterprise::Railtie` to correctly register rake
tasks in the `enterprise` namespace.
Previously, rake tasks under `enterprise/lib/tasks` were being eagerly
loaded at Rails boot, causing `undefined method 'namespace'` errors.
With this change, rake tasks are now registered only in the rake
context, avoiding boot-time issues and ensuring they are discoverable
with `bin/rake -T`.
**Tasks added:**
* `search:all` → Reindex messages for all accounts
* `search:account[ID]` → Reindex messages for a specific account
Fixes: #12414
Co-authored-by: Sojan Jose <sojan@pepalo.com>
