feat: add per-provider allow_user_refund control and align wildcard matching

allow_user_refund:
- Add allow_user_refund field to PaymentProviderInstance ent schema
- Migration 103: ALTER TABLE payment_provider_instances ADD COLUMN
- Cascade logic: disabling refund_enabled auto-disables allow_user_refund
- User refund validation: check provider instance allows user refund
- Admin refund validation: check provider instance allows admin refund
- Subscription refund: deduct days on refund, rollback on failure
- New endpoint: GET /payment/orders/refund-eligible-providers
- Frontend: ToggleSwitch in ProviderCard/Dialog, cascade in SettingsView

Wildcard matching:
- Change findPricingForModel from "longest prefix wins" to "config order
  priority (first match wins)", aligning with channel service behavior

backend/ent/paymentproviderinstance_create.go

@@ -132,6 +132,20 @@ func (_c *PaymentProviderInstanceCreate) SetNillableRefundEnabled(v *bool) *Paym
 	return _c
 }
 
+// SetAllowUserRefund sets the "allow_user_refund" field.
+func (_c *PaymentProviderInstanceCreate) SetAllowUserRefund(v bool) *PaymentProviderInstanceCreate {
+	_c.mutation.SetAllowUserRefund(v)
+	return _c
+}
+
+// SetNillableAllowUserRefund sets the "allow_user_refund" field if the given value is not nil.
+func (_c *PaymentProviderInstanceCreate) SetNillableAllowUserRefund(v *bool) *PaymentProviderInstanceCreate {
+	if v != nil {
+		_c.SetAllowUserRefund(*v)
+	}
+	return _c
+}
+
 // SetCreatedAt sets the "created_at" field.
 func (_c *PaymentProviderInstanceCreate) SetCreatedAt(v time.Time) *PaymentProviderInstanceCreate {
 	_c.mutation.SetCreatedAt(v)
@@ -223,6 +237,10 @@ func (_c *PaymentProviderInstanceCreate) defaults() {
 		v := paymentproviderinstance.DefaultRefundEnabled
 		_c.mutation.SetRefundEnabled(v)
 	}
+	if _, ok := _c.mutation.AllowUserRefund(); !ok {
+		v := paymentproviderinstance.DefaultAllowUserRefund
+		_c.mutation.SetAllowUserRefund(v)
+	}
 	if _, ok := _c.mutation.CreatedAt(); !ok {
 		v := paymentproviderinstance.DefaultCreatedAt()
 		_c.mutation.SetCreatedAt(v)
@@ -282,6 +300,9 @@ func (_c *PaymentProviderInstanceCreate) check() error {
 	if _, ok := _c.mutation.RefundEnabled(); !ok {
 		return &ValidationError{Name: "refund_enabled", err: errors.New(`ent: missing required field "PaymentProviderInstance.refund_enabled"`)}
 	}
+	if _, ok := _c.mutation.AllowUserRefund(); !ok {
+		return &ValidationError{Name: "allow_user_refund", err: errors.New(`ent: missing required field "PaymentProviderInstance.allow_user_refund"`)}
+	}
 	if _, ok := _c.mutation.CreatedAt(); !ok {
 		return &ValidationError{Name: "created_at", err: errors.New(`ent: missing required field "PaymentProviderInstance.created_at"`)}
 	}
@@ -351,6 +372,10 @@ func (_c *PaymentProviderInstanceCreate) createSpec() (*PaymentProviderInstance,
 		_spec.SetField(paymentproviderinstance.FieldRefundEnabled, field.TypeBool, value)
 		_node.RefundEnabled = value
 	}
+	if value, ok := _c.mutation.AllowUserRefund(); ok {
+		_spec.SetField(paymentproviderinstance.FieldAllowUserRefund, field.TypeBool, value)
+		_node.AllowUserRefund = value
+	}
 	if value, ok := _c.mutation.CreatedAt(); ok {
 		_spec.SetField(paymentproviderinstance.FieldCreatedAt, field.TypeTime, value)
 		_node.CreatedAt = value
@@ -525,6 +550,18 @@ func (u *PaymentProviderInstanceUpsert) UpdateRefundEnabled() *PaymentProviderIn
 	return u
 }
 
+// SetAllowUserRefund sets the "allow_user_refund" field.
+func (u *PaymentProviderInstanceUpsert) SetAllowUserRefund(v bool) *PaymentProviderInstanceUpsert {
+	u.Set(paymentproviderinstance.FieldAllowUserRefund, v)
+	return u
+}
+
+// UpdateAllowUserRefund sets the "allow_user_refund" field to the value that was provided on create.
+func (u *PaymentProviderInstanceUpsert) UpdateAllowUserRefund() *PaymentProviderInstanceUpsert {
+	u.SetExcluded(paymentproviderinstance.FieldAllowUserRefund)
+	return u
+}
+
 // SetUpdatedAt sets the "updated_at" field.
 func (u *PaymentProviderInstanceUpsert) SetUpdatedAt(v time.Time) *PaymentProviderInstanceUpsert {
 	u.Set(paymentproviderinstance.FieldUpdatedAt, v)
@@ -715,6 +752,20 @@ func (u *PaymentProviderInstanceUpsertOne) UpdateRefundEnabled() *PaymentProvide
 	})
 }
 
+// SetAllowUserRefund sets the "allow_user_refund" field.
+func (u *PaymentProviderInstanceUpsertOne) SetAllowUserRefund(v bool) *PaymentProviderInstanceUpsertOne {
+	return u.Update(func(s *PaymentProviderInstanceUpsert) {
+		s.SetAllowUserRefund(v)
+	})
+}
+
+// UpdateAllowUserRefund sets the "allow_user_refund" field to the value that was provided on create.
+func (u *PaymentProviderInstanceUpsertOne) UpdateAllowUserRefund() *PaymentProviderInstanceUpsertOne {
+	return u.Update(func(s *PaymentProviderInstanceUpsert) {
+		s.UpdateAllowUserRefund()
+	})
+}
+
 // SetUpdatedAt sets the "updated_at" field.
 func (u *PaymentProviderInstanceUpsertOne) SetUpdatedAt(v time.Time) *PaymentProviderInstanceUpsertOne {
 	return u.Update(func(s *PaymentProviderInstanceUpsert) {
@@ -1073,6 +1124,20 @@ func (u *PaymentProviderInstanceUpsertBulk) UpdateRefundEnabled() *PaymentProvid
 	})
 }
 
+// SetAllowUserRefund sets the "allow_user_refund" field.
+func (u *PaymentProviderInstanceUpsertBulk) SetAllowUserRefund(v bool) *PaymentProviderInstanceUpsertBulk {
+	return u.Update(func(s *PaymentProviderInstanceUpsert) {
+		s.SetAllowUserRefund(v)
+	})
+}
+
+// UpdateAllowUserRefund sets the "allow_user_refund" field to the value that was provided on create.
+func (u *PaymentProviderInstanceUpsertBulk) UpdateAllowUserRefund() *PaymentProviderInstanceUpsertBulk {
+	return u.Update(func(s *PaymentProviderInstanceUpsert) {
+		s.UpdateAllowUserRefund()
+	})
+}
+
 // SetUpdatedAt sets the "updated_at" field.
 func (u *PaymentProviderInstanceUpsertBulk) SetUpdatedAt(v time.Time) *PaymentProviderInstanceUpsertBulk {
 	return u.Update(func(s *PaymentProviderInstanceUpsert) {