Update: Admin and User Management APIs Completed

What changed

• Admin user listing now supports search, filtering, and pagination.
• Admin user details now include sender IDs, API keys, and balance context.
• Admin credit adjustments now flow through ledger-backed operations.
• Sender ID moderation is validated and returns clearer errors.
• Users now have a dedicated /api/users/me read/update endpoint.

Why

Operations and support teams need reliable controls early in MVP, especially for credit and identity workflows.

Outcome

The admin/user API layer is now safer, more predictable, and easier to operate.