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/server.go

@@ -2,6 +2,9 @@ package web
 
 import (
 	"fmt"
+	"fuj-management/go/internal/config"
+	"fuj-management/go/internal/services/membership"
+	"fuj-management/go/internal/web/api"
 	"fuj-management/go/internal/web/middleware"
 	"log/slog"
 	"net/http"
@@ -15,9 +18,22 @@ type BuildInfo struct {
 }
 
 // Run registers routes and starts the HTTP server on addr.
-func Run(logger *slog.Logger, addr string, build BuildInfo) error {
+func Run(logger *slog.Logger, addr string, build BuildInfo, sources membership.Sources, cfg config.Config) error {
+	h := &api.Handler{
+		BuildVersion: build.Version,
+		BuildCommit:  build.Commit,
+		BuildDate:    build.BuildDate,
+		Sources:      sources,
+		Config:       cfg,
+		Logger:       logger,
+	}
+
 	mux := http.NewServeMux()
 	mux.HandleFunc("GET /{$}", helloHandler(build))
+	mux.HandleFunc("GET /api/version", h.ServeVersion)
+	mux.HandleFunc("GET /api/adults", h.ServeAdults)
+	mux.HandleFunc("GET /api/juniors", h.ServeJuniors)
+	mux.HandleFunc("GET /api/payments", h.ServePayments)
 
 	logger.Info("starting server", "addr", addr)
 	return http.ListenAndServe(addr, middleware.RequestTimer(logger, mux))