fix: resolve DNS hostnames in STEMEDB_SEED_NODES for k8s headless service

SocketAddr::parse() doesn't resolve DNS names. Use tokio::net::lookup_host
for k8s pod DNS (stemedb-{0,1,2}.stemedb-headless.stemedb.svc:18182).

crates/stemedb-cluster/src/bin/node.rs

@@ -38,7 +38,8 @@ struct NodeConfig {
 }
 
 impl NodeConfig {
-    fn from_env() -> Self {
+    /// Load config from env, resolving DNS hostnames in seed nodes.
+    async fn from_env() -> Self {
         let api_addr = std::env::var("STEMEDB_NODE_API_ADDR")
             .unwrap_or_else(|_| "127.0.0.1:18181".to_string())
             .parse()
@@ -49,12 +50,28 @@ impl NodeConfig {
             .parse()
             .unwrap_or_else(|_| SocketAddr::from(([127, 0, 0, 1], 18182)));
 
-        let seed_nodes = std::env::var("STEMEDB_SEED_NODES")
+        let raw_seeds = std::env::var("STEMEDB_SEED_NODES").unwrap_or_default();
-            .unwrap_or_default()
+        let mut seed_nodes = Vec::new();
-            .split(',')
+        for entry in raw_seeds.split(',').filter(|s| !s.trim().is_empty()) {
-            .filter(|s| !s.trim().is_empty())
+            let entry = entry.trim();
-            .filter_map(|s| s.trim().parse().ok())
+            // Try direct SocketAddr parse first (e.g., "10.0.0.1:18182")
-            .collect();
+            if let Ok(addr) = entry.parse::<SocketAddr>() {
+                seed_nodes.push(addr);
+            } else {
+                // DNS hostname (e.g., "stemedb-0.stemedb-headless.stemedb.svc:18182")
+                match tokio::net::lookup_host(entry).await {
+                    Ok(mut addrs) => {
+                        if let Some(addr) = addrs.next() {
+                            info!(seed = entry, resolved = %addr, "Resolved seed node");
+                            seed_nodes.push(addr);
+                        }
+                    }
+                    Err(e) => {
+                        info!(seed = entry, error = %e, "Failed to resolve seed (may not be up yet)");
+                    }
+                }
+            }
+        }
 
         let num_shards =
             std::env::var("STEMEDB_NUM_SHARDS").ok().and_then(|s| s.parse().ok()).unwrap_or(4);
@@ -80,7 +97,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     tracing_subscriber::registry().with(env_filter).with(tracing_subscriber::fmt::layer()).init();
 
-    let config = NodeConfig::from_env();
+    let config = NodeConfig::from_env().await;
 
     // Use stable NodeId (env var → hostname → random fallback)
     let node_id = stable_node_id();