fix(payments,portfolio,scheduling): add ID validation hardening

Add validators.IsValidID() checks on URL param IDs to return 404 instead of 400 for invalid IDs. Add offset cap and query length limit in portfolio images handler.

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

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

backend/handlers/payments/handlers.go

@@ -2,6 +2,7 @@ package payments
 
 import (
 	"crussell/internal/square"
+	"crussell/internal/validators"
 	"crussell/mw"
 	"encoding/json"
 	"errors"
@@ -87,8 +88,8 @@ type PaymentSummaryResponse struct {
 
 func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 	bookingID := chi.URLParam(r, "id")
-	if bookingID == "" {
-		http.Error(w, "Booking ID is required", http.StatusBadRequest)
+	if bookingID == "" || !validators.IsValidID(bookingID) {
+		http.Error(w, "Booking not found", http.StatusNotFound)
 		return
 	}
 
@@ -260,8 +261,8 @@ func GetCheckoutStatus(w http.ResponseWriter, r *http.Request) {
 
 func CreateBookingPayment(w http.ResponseWriter, r *http.Request) {
 	bookingID := chi.URLParam(r, "id")
-	if bookingID == "" {
-		http.Error(w, "Booking ID is required", http.StatusBadRequest)
+	if bookingID == "" || !validators.IsValidID(bookingID) {
+		http.Error(w, "Booking not found", http.StatusNotFound)
 		return
 	}
 
@@ -459,8 +460,8 @@ func GetUserPaymentMethods(w http.ResponseWriter, r *http.Request) {
 
 func DeletePaymentMethod(w http.ResponseWriter, r *http.Request) {
 	cardID := chi.URLParam(r, "id")
-	if cardID == "" {
-		http.Error(w, "Card ID is required", http.StatusBadRequest)
+	if cardID == "" || !validators.IsValidID(cardID) {
+		http.Error(w, "Payment method not found", http.StatusNotFound)
 		return
 	}
 
@@ -524,8 +525,8 @@ func CreatePaymentMethod(w http.ResponseWriter, r *http.Request) {
 
 func RefundPayment(w http.ResponseWriter, r *http.Request) {
 	paymentID := chi.URLParam(r, "payment_id")
-	if paymentID == "" {
-		http.Error(w, "Payment ID is required", http.StatusBadRequest)
+	if paymentID == "" || !validators.IsValidID(paymentID) {
+		http.Error(w, "Payment not found", http.StatusNotFound)
 		return
 	}
 
@@ -640,8 +641,8 @@ func RefundPayment(w http.ResponseWriter, r *http.Request) {
 
 func CreateTipPayment(w http.ResponseWriter, r *http.Request) {
 	bookingID := chi.URLParam(r, "id")
-	if bookingID == "" {
-		http.Error(w, "Booking ID is required", http.StatusBadRequest)
+	if bookingID == "" || !validators.IsValidID(bookingID) {
+		http.Error(w, "Booking not found", http.StatusNotFound)
 		return
 	}
 
@@ -753,8 +754,8 @@ func CreateTipPayment(w http.ResponseWriter, r *http.Request) {
 
 func GetBookingPaymentSummary(w http.ResponseWriter, r *http.Request) {
 	bookingID := chi.URLParam(r, "id")
-	if bookingID == "" {
-		http.Error(w, "Booking ID is required", http.StatusBadRequest)
+	if bookingID == "" || !validators.IsValidID(bookingID) {
+		http.Error(w, "Booking not found", http.StatusNotFound)
 		return
 	}