chore: run go fix for Go 1.26 modernization

106 files: interface{}→any, strings.Split→SplitSeq, CutPrefix/Cut, strings.Builder, slices.Contains, remove redundant // +build directives, gofmt import ordering and indentation.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/bookings/edit_requests_test.go

@@ -1,5 +1,4 @@
 //go:build test && dev
-// +build test,dev
 
 package bookings
 
@@ -34,8 +33,8 @@ import (
 
 	"crussell/clock"
 	"crussell/db"
-	"crussell/testutils"
 	"crussell/mw"
+	"crussell/testutils"
 	"crussell/testutils/fixtures"
 	"crussell/testutils/jwt"
 
@@ -1610,8 +1609,6 @@ func TestAdminApproveEditRequestHandler_WithNotesOnly(t *testing.T) {
 func TestAdminApproveEditRequestHandler_OverlapWithBooking(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 
-
-
 	userID, err := fixtures.CreateTestUser(tx)
 	if err != nil {
 		t.Fatalf("failed to create user: %v", err)
@@ -1883,8 +1880,6 @@ func TestUserCancelBookingHandler_CleansUpEditRequest(t *testing.T) {
 func TestAdminApproveEditRequestHandler_BlockedByExceptionalClosedHours(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 
-
-
 	_, serviceID, bookingID, token := setupEditRequestTest(t, ctx, tx)
 	_ = serviceID