Enterprise plan, monthly usage, and stability

A big bundle of new features and improvements:

New

• Enterprise plan for teams with higher-volume needs.
• Month-by-month usage breakdown on the usage page.

Improved

• Clearer login instructions and password requirements when setting up transcriptions.
• More reliable WhatsApp connections: reworked session management and more robust reconnection after drops.
• Mobile interface polish (tabs, tables, and pagination).

Fixed

• The checkout button is now disabled when you already have an active subscription.
• Subscription cancellations use unique idempotency keys to avoid duplicate requests.