feat(config): integrate etcd for service discovery and config management

- Add etcd-client dependency for distributed configuration storage
- Implement EtcdConfig with priority: etcd > environment variables > defaults
- Add ServiceRegistry for service registration with lease keep-alive
- Integrate etcd-based service discovery for appks gRPC connections
- Add service watcher for real-time service instance updates
- Migrate Redis configuration from single URL to cluster node list
- Update Dockerfile with default IMKS_HOST and IMKS_PORT environment variables
- Add etcd bootstrap configuration through environment variables
- Implement Redis cluster URL building with optional authentication

telemetry/config.rs

@@ -32,10 +32,7 @@ impl Default for TelemetryConfig {
         Self {
             service_name: env_or("OTEL_SERVICE_NAME", "imks"),
             service_version: env_or("OTEL_SERVICE_VERSION", env!("CARGO_PKG_VERSION")),
-            otlp_endpoint: env_or(
-                "OTEL_EXPORTER_OTLP_ENDPOINT",
-                "http://localhost:4317",
-            ),
+            otlp_endpoint: env_or("OTEL_EXPORTER_OTLP_ENDPOINT", "http://localhost:4317"),
             otlp_protocol: detect_otlp_protocol(),
             traces_enabled: env_bool("OTEL_TRACES_ENABLED", true),
             metrics_enabled: env_bool("OTEL_METRICS_ENABLED", true),