Add `status` filter to List Subscriptions API

[stilla]

from the ticket

The List Subscriptions endpoint (GET /v1/subscriptions) currently does not support filtering by subscription status.

Requested Change

Add a status query parameter to allow filtering subscriptions by their status (e.g. active, trialing, canceled, past_due).

Use Case

Developers need to retrieve only active or trialing subscriptions without fetching all subscriptions and filtering client-side. This is a common need when syncing subscription state or building dashboards.

_{Sent by @rishi-raj-jain from Add status field to subscriptions list.}