feat(go): M5.2 — HTTP handlers for /api/adults, /api/juniors, /api/payments, /api/version

- Add web/api/handler.go: Handler struct wiring Sources+Config into ServeAdults,
  ServeJuniors, ServePayments, ServeVersion
- Add web/api/build_common.go: getMonthLabels, groupRawPaymentsByPerson, settledBalance,
  domain-to-wire converters, ensureSlice generic helper
- Add web/api/build_adults.go: buildAdultsResponse + buildAdultMemberRow mirroring
  scripts/views.py:build_adults_view_model
- Add web/api/build_juniors.go: buildJuniorsResponse + buildJuniorMemberRow mirroring
  scripts/views.py:build_juniors_view_model, including "?" sentinel and :NJ,MA breakdown
- Add web/api/build_payments.go: buildPaymentsResponse with Unmatched/Unknown bucket
- Extend reconcile.FeeData/MonthData with IsUnknown, JuniorAttendance, AdultAttendance
- Extend reconcile.Transaction with ManualFix, VS, BankID, SyncID for raw_payments wire field
- Export membership.AdultMergedMonths and JuniorMergedMonths
- Update sources.go to propagate new FeeData fields and parse extra transaction columns
- Wire sources+cfg into web.Run; register /api/* routes via Go 1.22 method+path patterns
- Fix pre-existing gofumpt formatting in fio_test.go and fio_table.go

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

go/internal/web/api/handler.go

@@ -0,0 +1,125 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"fuj-management/go/internal/config"
+	"fuj-management/go/internal/services/membership"
+	"log/slog"
+	"net/http"
+	"time"
+
+	domreconcile "fuj-management/go/internal/domain/reconcile"
+)
+
+// Handler holds the shared dependencies for all /api/* routes.
+type Handler struct {
+	BuildVersion string
+	BuildCommit  string
+	BuildDate    string
+	Sources      membership.Sources
+	Config       config.Config
+	Logger       *slog.Logger
+}
+
+// ServeVersion handles GET /api/version.
+func (h *Handler) ServeVersion(w http.ResponseWriter, r *http.Request) {
+	writeJSON(w, VersionResponse{
+		Tag:       h.BuildVersion,
+		Commit:    h.BuildCommit,
+		BuildDate: h.BuildDate,
+	})
+}
+
+// ServeAdults handles GET /api/adults.
+func (h *Handler) ServeAdults(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	members, sortedMonths, txns, exceptions, err := h.loadAll(ctx, true)
+	if err != nil {
+		h.writeError(w, r, err)
+		return
+	}
+	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
+	writeJSON(w, buildAdultsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")))
+}
+
+// ServeJuniors handles GET /api/juniors.
+func (h *Handler) ServeJuniors(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	members, sortedMonths, txns, exceptions, err := h.loadAll(ctx, false)
+	if err != nil {
+		h.writeError(w, r, err)
+		return
+	}
+	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
+	writeJSON(w, buildJuniorsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")))
+}
+
+// ServePayments handles GET /api/payments.
+func (h *Handler) ServePayments(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	txns, err := h.Sources.LoadTransactions(ctx)
+	if err != nil {
+		h.writeError(w, r, fmt.Errorf("load transactions: %w", err))
+		return
+	}
+	writeJSON(w, buildPaymentsResponse(txns, h.allMemberNames(ctx)))
+}
+
+func (h *Handler) loadAll(ctx context.Context, adults bool) (
+	members []domreconcile.Member,
+	sortedMonths []string,
+	txns []domreconcile.Transaction,
+	exceptions map[domreconcile.ExceptionKey]domreconcile.Exception,
+	err error,
+) {
+	if adults {
+		members, sortedMonths, err = h.Sources.LoadAdults(ctx)
+	} else {
+		members, sortedMonths, err = h.Sources.LoadJuniors(ctx)
+	}
+	if err != nil {
+		err = fmt.Errorf("load members: %w", err)
+		return
+	}
+	txns, err = h.Sources.LoadTransactions(ctx)
+	if err != nil {
+		err = fmt.Errorf("load transactions: %w", err)
+		return
+	}
+	exceptions, err = h.Sources.LoadExceptions(ctx)
+	if err != nil {
+		err = fmt.Errorf("load exceptions: %w", err)
+	}
+	return
+}
+
+func (h *Handler) allMemberNames(ctx context.Context) []string {
+	var names []string
+	if adults, _, err := h.Sources.LoadAdults(ctx); err == nil {
+		for _, m := range adults {
+			names = append(names, m.Name)
+		}
+	}
+	if juniors, _, err := h.Sources.LoadJuniors(ctx); err == nil {
+		for _, m := range juniors {
+			names = append(names, m.Name)
+		}
+	}
+	return names
+}
+
+func (h *Handler) writeError(w http.ResponseWriter, r *http.Request, err error) {
+	if h.Logger != nil {
+		h.Logger.Error("api error", "path", r.URL.Path, "err", err)
+	}
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(http.StatusInternalServerError)
+	_ = json.NewEncoder(w).Encode(map[string]string{"error": err.Error()})
+}
+
+func writeJSON(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	_ = json.NewEncoder(w).Encode(v)
+}