Populate payment method filter from real data instead of a guessed list

The previous fix hardcoded apple_pay/google_pay as extra filter options,
but Payment.method is free-text set by whatever the gateway reports, so
guessing at literal values was fragile and still didn't surface them for
this user. Add GET /api/payments/mypayments/methods returning the
distinct method values actually present in the user's payments, and have
the dashboard filter build its options from that instead. Also switch
the method filter from a startsWith match to an exact match, since the
values now come straight from the same column being filtered.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/controllers/paymentController.js

@@ -369,7 +369,7 @@ const getUserPayments = async (req, res) => {
     };
 
     if (req.query.method) {
-      where.method = { startsWith: String(req.query.method), mode: 'insensitive' };
+      where.method = { equals: String(req.query.method), mode: 'insensitive' };
     }
 
     if (req.query.kind === 'refund') {
@@ -405,6 +405,33 @@ const getUserPayments = async (req, res) => {
   }
 };
 
+// @desc    Get the distinct payment methods actually present in the user's own payments,
+//          so the dashboard filter never has to guess at gateway-reported values
+//          (e.g. apple_pay, google_pay) — it only ever offers what's really there.
+// @route   GET /api/payments/mypayments/methods
+// @access  Private
+const getUserPaymentMethods = async (req, res) => {
+  try {
+    const rows = await prisma.payment.findMany({
+      where: {
+        isDonation: false,
+        method: { not: null },
+        OR: [
+          { userId: req.user.id },
+          { registration: { userId: req.user.id } }
+        ]
+      },
+      distinct: ['method'],
+      select: { method: true },
+      orderBy: { method: 'asc' }
+    });
+
+    res.json({ methods: rows.map(r => r.method).filter(Boolean) });
+  } catch (error) {
+    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
+  }
+};
+
 // @desc    Get payment by ID
 // @route   GET /api/payments/:id
 // @access  Private
@@ -1224,6 +1251,7 @@ module.exports = {
   createPayment,
   getPayments,
   getUserPayments,
+  getUserPaymentMethods,
   getPaymentById,
   getPaymentsByRegistration,
   getPaymentsByEvent,