feat(go): M6.2 — adults page (table, filters, credits/debts/unmatched, Pay buttons)

- Extract AssembleAdults(ctx) from ServeAdults so HTML and JSON API share one reconcile path.
- HTMLHandler gains *api.Handler; ServeAdults loads real data and renders adults.tmpl.
- AdultsPageData view model + qrHref/qrHrefAll funcMap (URL-encode /qr params, YYYY-MM→MM/YYYY).
- adults.tmpl: full reconcile table, per-cell status classes + cell-unpaid-current, Pay button hrefs,
  totals row, credits/debts/unmatched sections, filter controls, sheet links.
- static/js/filters.js: NFD-normalize name filter + month-range column hiding; future months hidden by default.
- TestAdultsPage asserts member name and cell text against fixture data.

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

go/internal/web/render.go

@@ -2,9 +2,12 @@ package web
 
 import (
 	"fmt"
+	"fuj-management/go/internal/web/api"
 	"html/template"
 	"log/slog"
 	"net/http"
+	"net/url"
+	"strconv"
 )
 
 // PageData is the view model passed to every HTML template.
@@ -13,6 +16,13 @@ type PageData struct {
 	Build  BuildInfo
 }
 
+// AdultsPageData is the view model for the /adults HTML page.
+type AdultsPageData struct {
+	PageData
+	Data  api.AdultsResponse
+	Error string
+}
+
 // Renderer parses and executes HTML templates from the embedded FS.
 type Renderer struct {
 	tmpls map[string]*template.Template
@@ -20,12 +30,43 @@ type Renderer struct {
 
 var pageNames = []string{"adults", "juniors", "payments", "sync", "flush_cache"}
 
+// qrHref builds the /qr query URL for a single-month Pay button.
+// rawMonth is "YYYY-MM"; it is converted to "MM/YYYY" in the QR message.
+func qrHref(account string, amount int, name, rawMonth string) string {
+	// Convert "YYYY-MM" → "MM/YYYY" to match Python's showPayQR JS.
+	if len(rawMonth) == 7 && rawMonth[4] == '-' {
+		rawMonth = rawMonth[5:] + "/" + rawMonth[:4]
+	}
+	msg := name + ": " + rawMonth
+	return "/qr?" + url.Values{
+		"account": {account},
+		"amount":  {strconv.Itoa(amount)},
+		"message": {msg},
+	}.Encode()
+}
+
+// qrHrefAll builds the /qr query URL for a Pay-All button.
+// rawPeriods is the "+" -joined MM/YYYY string from MemberRow.RawUnpaidPeriods.
+func qrHrefAll(account string, amount int, name, rawPeriods string) string {
+	msg := name + ": " + rawPeriods
+	return "/qr?" + url.Values{
+		"account": {account},
+		"amount":  {strconv.Itoa(amount)},
+		"message": {msg},
+	}.Encode()
+}
+
+var tmplFuncs = template.FuncMap{
+	"qrHref":    qrHref,
+	"qrHrefAll": qrHrefAll,
+}
+
 // NewRenderer parses all templates from the embedded FS.
 // A parse failure should be treated as a startup-time fatal error.
 func NewRenderer() (*Renderer, error) {
 	tmpls := make(map[string]*template.Template, len(pageNames))
 	for _, name := range pageNames {
-		t, err := template.New("").ParseFS(templateFS,
+		t, err := template.New("").Funcs(tmplFuncs).ParseFS(templateFS,
 			"templates/base.tmpl",
 			"templates/partials/nav.tmpl",
 			"templates/partials/footer.tmpl",