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

svc/deploy.rs

@@ -10,8 +10,11 @@ use std::env;
 pub struct DeployConfig {
     /// "local" | "redis" | "nats"
     pub adapter_mode: String,
-    /// Redis connection URL (used when adapter_mode = "redis").
-    pub redis_url: String,
+    /// Redis cluster nodes, comma-separated host:port pairs.
+    /// Example: "redis1:6379,redis2:6379,redis3:6379"
+    pub redis_cluster_nodes: String,
+    /// Redis password (optional).
+    pub redis_password: String,
     /// NATS connection URL (used when adapter_mode = "nats").
     pub nats_url: String,
     /// Unique server ID for this node.
@@ -32,8 +35,9 @@ impl DeployConfig {
 
         Self {
             adapter_mode: env::var("IMKS_ADAPTER").unwrap_or_else(|_| "local".into()),
-            redis_url: env::var("IMKS_REDIS_URL")
-                .unwrap_or_else(|_| "redis://localhost:6379".into()),
+            redis_cluster_nodes: env::var("IMKS_REDIS_CLUSTER_NODES")
+                .unwrap_or_else(|_| "localhost:6379,localhost:6380,localhost:6381".into()),
+            redis_password: env::var("IMKS_REDIS_PASSWORD").unwrap_or_default(),
             nats_url: env::var("IMKS_NATS_URL").unwrap_or_else(|_| "nats://localhost:4222".into()),
             server_id,
             webtransport_enabled: env::var("IMKS_WT_ENABLED")
@@ -47,6 +51,17 @@ impl DeployConfig {
             key_path: env::var("IMKS_WT_KEY_PATH").unwrap_or_default(),
         }
     }
+
+    /// Build a redis-cluster URL from cluster_nodes and optional password.
+    /// Format: redis-cluster://[:password@]host1:port1,host2:port2,...
+    pub fn redis_cluster_url(&self) -> String {
+        let auth = if self.redis_password.is_empty() {
+            String::new()
+        } else {
+            format!(":{}@", self.redis_password)
+        };
+        format!("redis-cluster://{}{}", auth, self.redis_cluster_nodes)
+    }
 }
 
 impl Default for DeployConfig {