Named rate-limit configurations reset the limiter on every request #2816

When LimitHandler uses a custom configuration name, LimitConfig.load(customName) creates a new object on every call. The handler treats an object identity change as a configuration reload and replaces its rate limiter. Repeated requests can therefore reset the quota even when the underlying configuration has not changed.

The default limit name has a cache keyed by the identity of its configuration map; custom names bypass that cache.

Source paths:

• limit-config/src/main/java/com/networknt/limit/LimitConfig.java, load(String)
• rate-limit/src/main/java/com/networknt/limit/LimitHandler.java, configuration identity/reload handling

Acceptance:

• Reproduce using a named configuration and repeated requests within one quota window.
• Keep the same limiter when the named configuration is unchanged.
• Apply changed named configurations through the supported reload path.
• Cover independent named configurations, default-name behavior, and reload isolation.

Discovered during the Jackson 3 migration review of #2815. This production bug is not repaired by that PR's fixture changes and needs a separately scoped fix. The current evidence is source inspection; do not infer a deployed-service reproduction.