style(backend): modernize Go syntax with range-over-int and type inference

Use Go 1.22+ range-over-integer syntax, replace interface{} with any,
and remove redundant type parameters.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

4 files changed, 6 insertions, 6 deletions

diff --git a/backend/admin/handler.go b/backend/admin/handler.go
index 9bdeb69..8eac425 100644
--- a/backend/admin/handler.go
+++ b/backend/admin/handler.go
@@ -1145,9 +1145,9 @@ func (h *Handler) postTournamentNew(c echo.Context) error {
 			return err
 		}
 		// Create match slots for all rounds
-		for round := 0; round < numRounds; round++ {
+		for round := range numRounds {
 			numPositions := bracketSize / (1 << (round + 1))
-			for pos := 0; pos < numPositions; pos++ {
+			for pos := range numPositions {
 				if err := qtx.CreateTournamentMatch(ctx, db.CreateTournamentMatchParams{
 					TournamentID: tournamentID,
 					Round:        int32(round),
diff --git a/backend/admin/handler_test.go b/backend/admin/handler_test.go
index 7249c2b..9de9a0b 100644
--- a/backend/admin/handler_test.go
+++ b/backend/admin/handler_test.go
@@ -338,7 +338,7 @@ type mockRenderer struct {
 	lastData         any
 }
 
-func (r *mockRenderer) Render(_ io.Writer, name string, data interface{}, _ echo.Context) error {
+func (r *mockRenderer) Render(_ io.Writer, name string, data any, _ echo.Context) error {
 	r.lastTemplateName = name
 	r.lastData = data
 	return nil
diff --git a/backend/api/handler.go b/backend/api/handler.go
index 4105efc..8d0d9be 100644
--- a/backend/api/handler.go
+++ b/backend/api/handler.go
@@ -554,9 +554,9 @@ func (h *Handler) GetTournament(ctx context.Context, request GetTournamentReques
 	}
 	resultByKey := make(map[matchKey]*matchResult)
 
-	for round := 0; round < numRounds; round++ {
+	for round := range numRounds {
 		numPositions := bracketSize / (1 << (round + 1))
-		for pos := 0; pos < numPositions; pos++ {
+		for pos := range numPositions {
 			m, exists := matchByKey[matchKey{round, pos}]
 			mr := &matchResult{}
 
diff --git a/backend/api/handler_test.go b/backend/api/handler_test.go
index a3ca3fb..2415710 100644
--- a/backend/api/handler_test.go
+++ b/backend/api/handler_test.go
@@ -729,7 +729,7 @@ func TestGetGameWatchLatestStates_Empty(t *testing.T) {
 
 func TestToNullableWith(t *testing.T) {
 	t.Run("nil value", func(t *testing.T) {
-		result := toNullableWith[int, string](nil, func(_ int) string { return "x" })
+		result := toNullableWith(nil, func(_ int) string { return "x" })
 		if !result.IsNull() {
 			t.Error("expected null for nil input")
 		}