fix(service): keep chunk capacity math from overflowing

chunkStrings/chunkInts sized their result with (len+size-1)/size, so a
size near MaxInt wrapped negative and make panicked with "cap out of
range"; count the chunks with div+remainder instead. NormalizeUDPHop's
len-hops+1 is bounded by len(masks) since hops >= 1, so cap at that.

Resolves CodeQL go/allocation-size-overflow alerts #119 and #120.

internal/web/service/inbound_util_test.go

@@ -1,6 +1,10 @@
 package service
 
-import "testing"
+import (
+	"math"
+	"slices"
+	"testing"
+)
 
 func TestNormalizeSubSortIndex(t *testing.T) {
 	cases := []struct {
@@ -18,3 +22,15 @@ func TestNormalizeSubSortIndex(t *testing.T) {
 		}
 	}
 }
+
+// A size near MaxInt used to overflow the capacity math and panic in make (CodeQL #119).
+func TestChunkHugeSizeKeepsOneBatch(t *testing.T) {
+	strs := []string{"a", "b", "c"}
+	if got := chunkStrings(strs, math.MaxInt); len(got) != 1 || !slices.Equal(got[0], strs) {
+		t.Fatalf("chunkStrings(MaxInt) = %v, want [%v]", got, strs)
+	}
+	ints := []int{1, 2, 3}
+	if got := chunkInts(ints, math.MaxInt); len(got) != 1 || !slices.Equal(got[0], ints) {
+		t.Fatalf("chunkInts(MaxInt) = %v, want [%v]", got, ints)
+	}
+}