Returns high-level metrics about the cryptographic key inventory:

• Total keys by status (ACTIVE, ROTATED, EXPIRED, REVOKED)
• Keys in warning period (soft expiration reached)
• Keys approaching usage limits
• Total usage count across all keys, served with the usageWindow it is measured
  over (ALL_TIME) and the i18n key naming it, because a second screen renders a
  figure under the same label and a total that does not say which span it covers
  cannot be compared with anything

This endpoint is designed for CISO dashboards and security monitoring.

Authorization:
• Tenant admins: view own tenant's analytics only
• Platform admins: view any tenant's analytics

Path Parameter Validation:
The tenantId in the URL must match the JWT tenantId claim
(unless authenticated as platform admin with PLATFORM.ROOT scope).