feat(go/M2.11-12): wire fuj fees + fuj reconcile subcommands

Add internal/services/membership package: AttendanceLoader,
TransactionLoader, ExceptionLoader interfaces + NewStubSources stub
(returns ErrIOPending until M4 lands real Sheets loaders).

FeesReport and ReconcileReport orchestrate domain/fees + domain/reconcile
and write fixed-width text reports matching Python calculate_fees.py and
match_payments.py print_report output. 13 unit tests cover all formatter
branches and orchestration wiring via fake loaders.

cmd/fuj/main.go: fees and reconcile subcommands now dispatch; sync/infer
retain the [M4] placeholder.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

go/internal/services/membership/reconcile_test.go

@@ -0,0 +1,68 @@
+package membership
+
+import (
+	"bytes"
+	"context"
+	"fuj-management/go/internal/domain/reconcile"
+	"strings"
+	"testing"
+)
+
+type fakeSources struct {
+	members    []reconcile.Member
+	months     []string
+	txns       []reconcile.Transaction
+	exceptions map[reconcile.ExceptionKey]reconcile.Exception
+}
+
+func (f fakeSources) LoadAdults(_ context.Context) ([]reconcile.Member, []string, error) {
+	return f.members, f.months, nil
+}
+
+func (f fakeSources) LoadTransactions(_ context.Context) ([]reconcile.Transaction, error) {
+	return f.txns, nil
+}
+
+func (f fakeSources) LoadExceptions(_ context.Context) (map[reconcile.ExceptionKey]reconcile.Exception, error) {
+	return f.exceptions, nil
+}
+
+func TestReconcileReport(t *testing.T) {
+	t.Parallel()
+	s := fakeSources{
+		members: []reconcile.Member{
+			{Name: "Alice", Tier: "A", Fees: map[string]reconcile.FeeData{
+				"2026-04": {Expected: 700, Attendance: 3},
+			}},
+		},
+		months: []string{"2026-04"},
+		txns: []reconcile.Transaction{
+			{
+				Date: "2026-04-10", Amount: 700, Person: "Alice", Purpose: "2026-04",
+				Sender: "Alice Bank", Message: "fee",
+			},
+		},
+		exceptions: map[reconcile.ExceptionKey]reconcile.Exception{},
+	}
+
+	var buf bytes.Buffer
+	if err := ReconcileReport(context.Background(), s, 2026, &buf); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	got := buf.String()
+	if !strings.Contains(got, "PAYMENT RECONCILIATION REPORT") {
+		t.Error("missing report header")
+	}
+	if !strings.Contains(got, "OK") {
+		t.Errorf("expected 'OK' for fully-paid Alice, got:\n%s", got)
+	}
+}
+
+func TestReconcileReportStubErrors(t *testing.T) {
+	t.Parallel()
+	var buf bytes.Buffer
+	err := ReconcileReport(context.Background(), NewStubSources(), 2026, &buf)
+	if err == nil {
+		t.Fatal("expected error from stub, got nil")
+	}
+}