fix: EC shard copy address parsing and preserve .vif on volume destroy

Two bugs found during EC encoding + balancing test with 4 Rust volume servers:

1. VolumeEcShardsCopy manually split source_data_node on '.' which broke
   on IP addresses with dots. Now uses parse_grpc_address() like other RPCs.

2. remove_volume_files() deleted .vif files, breaking EC volumes that
   need the .vif after the original volume is destroyed. Matches Go's
   Destroy() which only removes .dat/.idx.

seaweed-volume/src/server/grpc_server.rs

@@ -1814,22 +1814,12 @@ impl VolumeServer for VolumeGrpcService {
 
         // Connect to source and copy shard files via CopyFile
         let source = &req.source_data_node;
-        // Parse source address: "ip:port.grpc_port"
-        let parts: Vec<&str> = source.split('.').collect();
-        if parts.len() != 2 {
-            return Err(Status::internal(format!(
-                "VolumeEcShardsCopy volume {} invalid source_data_node {}",
-                vid, source
-            )));
-        }
-        let grpc_addr = format!(
-            "{}:{}",
-            parts[0]
-                .rsplit_once(':')
-                .map(|(h, _)| h)
-                .unwrap_or(parts[0]),
-            parts[1]
-        );
+        let grpc_addr = parse_grpc_address(source).map_err(|e| {
+            Status::internal(format!(
+                "VolumeEcShardsCopy volume {} invalid source_data_node {}: {}",
+                vid, source, e
+            ))
+        })?;
 
         let channel = tonic::transport::Channel::from_shared(format!("http://{}", grpc_addr))
             .map_err(|e| {

seaweed-volume/src/storage/volume.rs

@@ -2167,7 +2167,10 @@ fn get_append_at_ns(last: u64) -> u64 {
 
 /// Remove all files associated with a volume.
 pub(crate) fn remove_volume_files(base: &str) {
-    for ext in &[".dat", ".idx", ".vif", ".sdx", ".cpd", ".cpx", ".note", ".rdb"] {
+    // Note: .vif is intentionally NOT deleted here — it must be preserved
+    // for EC volumes that reference it after the original volume is destroyed.
+    // Matches Go's volume.Destroy() which only removes .dat/.idx.
+    for ext in &[".dat", ".idx", ".sdx", ".cpd", ".cpx", ".note", ".rdb"] {
         let _ = fs::remove_file(format!("{}{}", base, ext));
     }
     // leveldb uses a directory