Read lastAppendAtNs from deleted V3 entries in integrity check

Go's doCheckAndFixVolumeData reads AppendAtNs from both live entries
(verifyNeedleIntegrity) and deleted tombstones (verifyDeletedNeedleIntegrity).
Rust was skipping deleted entries, which could result in a stale
last_append_at_ns if the last index entry is a deletion.

seaweed-volume/src/storage/volume.rs

@@ -1819,9 +1819,15 @@ impl Volume {
                 break;
             }
 
-            // If V3, try to read the append timestamp from the last verified entry
-            if version == VERSION_3 && !size.is_deleted() && size.0 > 0 {
-                let ts_offset = actual_offset + NEEDLE_HEADER_SIZE as u64 + size.0 as u64 + 4; // skip checksum
+            // If V3, try to read the append timestamp from the last verified entry.
+            // Go reads AppendAtNs from both live and deleted (tombstone) entries
+            // via verifyNeedleIntegrity and verifyDeletedNeedleIntegrity.
+            if version == VERSION_3 {
+                // For tombstones (deleted), body size on disk is 0.
+                // For live entries, body size is size.0.
+                let body_size = if size.is_deleted() { 0u64 } else { size.0 as u64 };
+                let ts_offset =
+                    actual_offset + NEEDLE_HEADER_SIZE as u64 + body_size + 4; // skip checksum
                 let mut ts_buf = [0u8; 8];
                 if self.read_exact_at_backend(&mut ts_buf, ts_offset).is_ok() {
                     let ts = u64::from_be_bytes(ts_buf);