Add ConfigReloadHandle with Arc<ArcSwap<DynamicConfig>> for lock-free reads
on the request hot path and tokio::sync::Mutex-serialized reload. Add static
config change detection via diff_static_config(). Add DynamicConfig validation
(rate_limit, body_limit, site checks). Add PartialEq derives to config types.
Include unit tests for ArcSwap swap visibility, invalid config rejection, and
concurrent reload serialization.
Add Clone derive to StaticConfig, ListenerConfig, TlsConfig, and
LoggingConfig to support immutable-after-startup pattern. Add unit
tests verifying TOML deserialization for multi-config (dedicated-IP)
and shared-IP (SAN certificate) deployment formats, default value
application, logging config, and site defaults.