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/mutation.go

@@ -15642,25 +15642,26 @@ func (m *PaymentOrderMutation) ResetEdge(name string) error {
 // PaymentProviderInstanceMutation represents an operation that mutates the PaymentProviderInstance nodes in the graph.
 type PaymentProviderInstanceMutation struct {
 	config
-	op              Op
-	typ             string
-	id              *int64
-	provider_key    *string
-	name            *string
-	_config         *string
-	supported_types *string
-	enabled         *bool
-	payment_mode    *string
-	sort_order      *int
-	addsort_order   *int
-	limits          *string
-	refund_enabled  *bool
-	created_at      *time.Time
-	updated_at      *time.Time
-	clearedFields   map[string]struct{}
-	done            bool
-	oldValue        func(context.Context) (*PaymentProviderInstance, error)
-	predicates      []predicate.PaymentProviderInstance
+	op                Op
+	typ               string
+	id                *int64
+	provider_key      *string
+	name              *string
+	_config           *string
+	supported_types   *string
+	enabled           *bool
+	payment_mode      *string
+	sort_order        *int
+	addsort_order     *int
+	limits            *string
+	refund_enabled    *bool
+	allow_user_refund *bool
+	created_at        *time.Time
+	updated_at        *time.Time
+	clearedFields     map[string]struct{}
+	done              bool
+	oldValue          func(context.Context) (*PaymentProviderInstance, error)
+	predicates        []predicate.PaymentProviderInstance
 }
 
 var _ ent.Mutation = (*PaymentProviderInstanceMutation)(nil)
@@ -16105,6 +16106,42 @@ func (m *PaymentProviderInstanceMutation) ResetRefundEnabled() {
 	m.refund_enabled = nil
 }
 
+// SetAllowUserRefund sets the "allow_user_refund" field.
+func (m *PaymentProviderInstanceMutation) SetAllowUserRefund(b bool) {
+	m.allow_user_refund = &b
+}
+
+// AllowUserRefund returns the value of the "allow_user_refund" field in the mutation.
+func (m *PaymentProviderInstanceMutation) AllowUserRefund() (r bool, exists bool) {
+	v := m.allow_user_refund
+	if v == nil {
+		return
+	}
+	return *v, true
+}
+
+// OldAllowUserRefund returns the old "allow_user_refund" field's value of the PaymentProviderInstance entity.
+// If the PaymentProviderInstance object wasn't provided to the builder, the object is fetched from the database.
+// An error is returned if the mutation operation is not UpdateOne, or the database query fails.
+func (m *PaymentProviderInstanceMutation) OldAllowUserRefund(ctx context.Context) (v bool, err error) {
+	if !m.op.Is(OpUpdateOne) {
+		return v, errors.New("OldAllowUserRefund is only allowed on UpdateOne operations")
+	}
+	if m.id == nil || m.oldValue == nil {
+		return v, errors.New("OldAllowUserRefund requires an ID field in the mutation")
+	}
+	oldValue, err := m.oldValue(ctx)
+	if err != nil {
+		return v, fmt.Errorf("querying old value for OldAllowUserRefund: %w", err)
+	}
+	return oldValue.AllowUserRefund, nil
+}
+
+// ResetAllowUserRefund resets all changes to the "allow_user_refund" field.
+func (m *PaymentProviderInstanceMutation) ResetAllowUserRefund() {
+	m.allow_user_refund = nil
+}
+
 // SetCreatedAt sets the "created_at" field.
 func (m *PaymentProviderInstanceMutation) SetCreatedAt(t time.Time) {
 	m.created_at = &t
@@ -16211,7 +16248,7 @@ func (m *PaymentProviderInstanceMutation) Type() string {
 // order to get all numeric fields that were incremented/decremented, call
 // AddedFields().
 func (m *PaymentProviderInstanceMutation) Fields() []string {
-	fields := make([]string, 0, 11)
+	fields := make([]string, 0, 12)
 	if m.provider_key != nil {
 		fields = append(fields, paymentproviderinstance.FieldProviderKey)
 	}
@@ -16239,6 +16276,9 @@ func (m *PaymentProviderInstanceMutation) Fields() []string {
 	if m.refund_enabled != nil {
 		fields = append(fields, paymentproviderinstance.FieldRefundEnabled)
 	}
+	if m.allow_user_refund != nil {
+		fields = append(fields, paymentproviderinstance.FieldAllowUserRefund)
+	}
 	if m.created_at != nil {
 		fields = append(fields, paymentproviderinstance.FieldCreatedAt)
 	}
@@ -16271,6 +16311,8 @@ func (m *PaymentProviderInstanceMutation) Field(name string) (ent.Value, bool) {
 		return m.Limits()
 	case paymentproviderinstance.FieldRefundEnabled:
 		return m.RefundEnabled()
+	case paymentproviderinstance.FieldAllowUserRefund:
+		return m.AllowUserRefund()
 	case paymentproviderinstance.FieldCreatedAt:
 		return m.CreatedAt()
 	case paymentproviderinstance.FieldUpdatedAt:
@@ -16302,6 +16344,8 @@ func (m *PaymentProviderInstanceMutation) OldField(ctx context.Context, name str
 		return m.OldLimits(ctx)
 	case paymentproviderinstance.FieldRefundEnabled:
 		return m.OldRefundEnabled(ctx)
+	case paymentproviderinstance.FieldAllowUserRefund:
+		return m.OldAllowUserRefund(ctx)
 	case paymentproviderinstance.FieldCreatedAt:
 		return m.OldCreatedAt(ctx)
 	case paymentproviderinstance.FieldUpdatedAt:
@@ -16378,6 +16422,13 @@ func (m *PaymentProviderInstanceMutation) SetField(name string, value ent.Value)
 		}
 		m.SetRefundEnabled(v)
 		return nil
+	case paymentproviderinstance.FieldAllowUserRefund:
+		v, ok := value.(bool)
+		if !ok {
+			return fmt.Errorf("unexpected type %T for field %s", value, name)
+		}
+		m.SetAllowUserRefund(v)
+		return nil
 	case paymentproviderinstance.FieldCreatedAt:
 		v, ok := value.(time.Time)
 		if !ok {
@@ -16483,6 +16534,9 @@ func (m *PaymentProviderInstanceMutation) ResetField(name string) error {
 	case paymentproviderinstance.FieldRefundEnabled:
 		m.ResetRefundEnabled()
 		return nil
+	case paymentproviderinstance.FieldAllowUserRefund:
+		m.ResetAllowUserRefund()
+		return nil
 	case paymentproviderinstance.FieldCreatedAt:
 		m.ResetCreatedAt()
 		return nil