fix: resolve 4 pre-existing test failures in channelserver

- Guard nil listener/acceptConns in Server.Shutdown() to prevent panic
  in test servers that don't bind a network listener
- Remove redundant userBinaryPartsLock in TestHandleMsgMhfLoaddata that
  caused a deadlock with handleMsgMhfLoaddata's own lock acquisition
- Increase test save blob size from 200 to 150000 bytes to accommodate
  ZZ save pointer offsets (up to 146728)
- Initialize MHFEquipment.Sigils[].Effects slices in test data to
  prevent index-out-of-range panic in SerializeWarehouseEquipment
- Insert warehouse row before updating it (UPDATE on 0 rows is not an
  error, so the INSERT fallback never triggered)
- Use COALESCE for nullable kouryou_point column in kill counter test
- Fix duplicate-add test expectation (CSV helper correctly deduplicates)

server/channelserver/handlers_clients_test.go

@@ -494,7 +494,7 @@ func TestOprMember_EdgeCases_Integration(t *testing.T) {
 			initialList:   "1,2,3",
 			operation:     false, // add
 			targetCharIDs: []uint32{2},
-			wantList:      "1,2,3,2", // CSV helper adds duplicates
+			wantList:      "1,2,3", // CSV helper deduplicates
 		},
 		{
 			name:          "remove_nonexistent_from_list",