#8 Issue 8: [Database] Provider Dashboard Stats

[elizabetheonoja-art]

Description:
Aggregate total energy sold and active meters for the Utility Company's admin panel.

Acceptance Criteria:

[ ] Endpoint GET /api/provider/stats.

[ ] Return: total_kwh_sold, total_revenue, active_meter_count.

[ ] Cache results for 5 minutes.

Priority: Low
Labels: admin, reporting