Returns keys approaching or exceeding a usage limit they are actually subject to:

• Keys above soft usage limit (advisory warning threshold)
• Keys above 75% of hard limit
• Keys above 90% of hard limit (critical)
• Usage percentage per key (usageCount / maxUsageLimit * 100)

Only keys with a POSITIVE maxUsageLimit are included. Under the platform sentinel
both 0 and null mean unlimited, and an unlimited key is stored as the literal
0 — so "has a value configured" is not the population, and a report built on that
reading returns the entire inventory.
Results are sorted by usage percentage descending (most critical first).

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).