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/payments/giftcards.go

@@ -11,8 +11,8 @@ import (
 	"strings"
 	"time"
 
-	"crussell/db"
 	"crussell/clock"
+	"crussell/db"
 	"crussell/internal/square"
 	"crussell/internal/validators"
 	"crussell/mw"
@@ -160,7 +160,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 	}
 
 	var gcTotal int
-	var gcListArgs []interface{}
+	var gcListArgs []any
 
 	gcListQuery := fmt.Sprintf(`
 		SELECT id, total_funds_added, amount_remaining, created_at, is_inventory
@@ -170,7 +170,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 
 	if searchTerm != "" {
 		searchPattern := "%" + searchTerm + "%"
-		gcListArgs = []interface{}{searchPattern}
+		gcListArgs = []any{searchPattern}
 
 		if cursorStr != "" {
 			cursorCreatedAt, cursorID, err := validators.ParseCursor(cursorStr)
@@ -202,7 +202,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 	// transaction (single connection).
 	gcTotal = 0
 	if whereSQL != "" {
-		countArgs := []interface{}{}
+		countArgs := []any{}
 		if searchTerm != "" {
 			countArgs = append(countArgs, "%"+searchTerm+"%")
 		}
@@ -243,7 +243,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 
 	var ubTotal int
 	var ubListQuery string
-	var ubListArgs []interface{}
+	var ubListArgs []any
 
 	if searchTerm != "" {
 		searchPattern := "%" + searchTerm + "%"
@@ -258,7 +258,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 			   OR u.email ILIKE $1
 			ORDER BY b.updated_at DESC
 		`
-		ubListArgs = []interface{}{searchPattern}
+		ubListArgs = []any{searchPattern}
 	} else {
 		ubListQuery = `
 			SELECT
@@ -267,7 +267,7 @@ func GetGiftCards(w http.ResponseWriter, r *http.Request) {
 			JOIN users u ON b.user_id = u.id
 			ORDER BY b.updated_at DESC
 		`
-		ubListArgs = []interface{}{}
+		ubListArgs = []any{}
 	}
 
 	ubRows, err := db.Conn.Query(ctx, ubListQuery, ubListArgs...)
@@ -736,7 +736,7 @@ func RedeemGiftCard(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.WriteHeader(http.StatusOK)
-	json.NewEncoder(w).Encode(map[string]interface{}{
+	json.NewEncoder(w).Encode(map[string]any{
 		"status":          "success",
 		"amount_redeemed": amountRemaining,
 	})
@@ -1065,7 +1065,7 @@ func BuyGiftCard(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.WriteHeader(http.StatusCreated)
-	json.NewEncoder(w).Encode(map[string]interface{}{
+	json.NewEncoder(w).Encode(map[string]any{
 		"status": "success",
 		"code":   cardID,
 		"amount": amountPounds,
@@ -1137,7 +1137,7 @@ func GetExpiredBalances(w http.ResponseWriter, r *http.Request) {
 		balances = []ExpiredBalance{}
 	}
 
-	json.NewEncoder(w).Encode(map[string]interface{}{
+	json.NewEncoder(w).Encode(map[string]any{
 		"expired_balances": balances,
 		"total":            len(balances),
 	})