Add ConfigServiceImpl and ConfigProtocol irpc enum behind feature flag

ConfigServiceImpl wraps ArcSwap<DynamicConfig> providing forwarding_policy(),
rate_limits(), and reload() methods for direct use (always available).
ConfigProtocol enum (GetForwardingPolicy, GetRateLimits, ReloadForwarding,
ReloadRateLimits) is gated behind the irpc feature flag per ADR-030.

crates/alknet-core/src/config/mod.rs

@@ -1,6 +1,8 @@
+pub mod config_service;
 pub mod dynamic_config;
 pub mod static_config;
 
+pub use config_service::ConfigServiceImpl;
 pub use dynamic_config::{
     new_dynamic_config, AuthPolicy, ConfigReloadHandle, DynamicConfig, ForwardingAction,
     ForwardingPolicy, ForwardingRule, RateLimitConfig,