panel: show the running version in the layout footer

Nothing in the UI said which build was running, though it is the value a
backup manifest is compared against on restore and the first thing worth
knowing when the panel misbehaves — it was only in the startup log line
and `panel -version`.

Add it as a small footer in the shared layout, supplied from render()
alongside .Active so no handler has to pass it, and gated on .User: the
login and setup pages face the internet and should not advertise a
version. Tests cover both the footer and render() supplying the key,
since neither is visible from any single handler.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/web/static/panel.css

@@ -63,6 +63,9 @@ td.actions { text-align: right; }
 @media (prefers-color-scheme: dark) { .code { background: #14171a !important; border-color: #2b3138 !important; } }
 h2 { font-size: 1.05rem; margin: 0 0 0.4rem; }
 .back { display: inline-block; margin-bottom: 1rem; }
+/* Build version, closing every authenticated page. Quiet on purpose: it is
+   reference material, not something to read on the way past. */
+.version { margin-top: 1.6rem; text-align: right; font-size: 0.8rem; color: #6b7280; }
 select, textarea {
   width: 100%; padding: 0.55rem 0.7rem; font-size: 1rem;
   border: 1px solid #cfd4da; border-radius: 6px; background: #fff; color: inherit;

internal/web/templates.go

@@ -79,10 +79,13 @@ func (s *Server) render(w http.ResponseWriter, status int, page string, data any
 	// The layout's navigation compares .Active against each item, so the key
 	// must exist on every authenticated page. Defaulting it here keeps a page
 	// that forgets it from failing to render — it simply highlights nothing.
+	// .Version, shown in the layout's footer, is supplied the same way: it is
+	// the same value on every page, so no handler should have to pass it.
 	if m, ok := data.(map[string]any); ok {
 		if _, has := m["Active"]; !has {
 			m["Active"] = ""
 		}
+		m["Version"] = s.cfg.Version
 	}
 	var buf bytes.Buffer
 	if err := tmpl.ExecuteTemplate(&buf, "layout.html", data); err != nil {

internal/web/templates/layout.html

@@ -19,6 +19,11 @@
 <main>
 {{if .User}}{{template "nav" .}}{{end}}
 {{template "content" .}}
+{{/* The running version, on every authenticated page: it is what a backup
+     manifest is checked against on restore and the first thing to establish
+     when something behaves unexpectedly. Only for signed-in administrators —
+     the login and setup pages must not advertise it to the internet. */}}
+{{if .User}}<footer class="version">SelfPost {{.Version}}</footer>{{end}}
 </main>
 </body>
 </html>{{end}}

internal/web/templates_test.go

@@ -3,6 +3,8 @@ package web
 import (
 	"bytes"
 	"io/fs"
+	"net/http"
+	"net/http/httptest"
 	"path"
 	"regexp"
 	"strings"
@@ -27,6 +29,68 @@ func TestEveryPageResolvesNav(t *testing.T) {
 	}
 }
 
+// The version comes from render(), not from each handler's data map, so the
+// footer is only correct as long as every page composes with the layout and
+// render keeps supplying the key. Both are asserted here rather than trusted.
+func TestLayoutShowsTheVersionOnlyWhenSignedIn(t *testing.T) {
+	tmpl, err := loadTemplates()
+	if err != nil {
+		t.Fatalf("loadTemplates: %v", err)
+	}
+	rendered := 0
+	for name := range tmpl.pages {
+		var buf bytes.Buffer
+		err := tmpl.pages[name].ExecuteTemplate(&buf, "layout.html", map[string]any{
+			"Title": "t", "User": "admin", "Active": "", "Version": "9.9.9-test",
+		})
+		if err != nil {
+			// Pages whose content block needs more data than this cannot be
+			// rendered here; the footer is in the shared layout, so one page
+			// that does render proves it for all of them.
+			continue
+		}
+		rendered++
+		if !strings.Contains(buf.String(), "SelfPost 9.9.9-test") {
+			t.Errorf("page %q does not show the version in the layout footer", name)
+		}
+	}
+	if rendered == 0 {
+		t.Fatal("no page rendered, so the footer was never actually checked")
+	}
+
+	// Signed out (login, setup) the version must not be advertised.
+	var buf bytes.Buffer
+	if err := tmpl.pages["login"].ExecuteTemplate(&buf, "layout.html", map[string]any{
+		"Title": "t", "Active": "", "Version": "9.9.9-test",
+	}); err != nil {
+		t.Fatalf("execute login: %v", err)
+	}
+	if strings.Contains(buf.String(), "9.9.9-test") {
+		t.Errorf("the login page shows the version to unauthenticated visitors:\n%s", buf.String())
+	}
+}
+
+func TestRenderSuppliesTheVersion(t *testing.T) {
+	tmpl, err := loadTemplates()
+	if err != nil {
+		t.Fatalf("loadTemplates: %v", err)
+	}
+	s := &Server{tmpl: tmpl, cfg: Config{Version: "9.9.9-test"}}
+	rec := httptest.NewRecorder()
+	data := map[string]any{"Title": "t", "User": "admin"}
+	s.render(rec, http.StatusOK, "backup", data)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200", rec.Code)
+	}
+	if got := data["Version"]; got != "9.9.9-test" {
+		t.Errorf("render did not supply Version (got %v)", got)
+	}
+	if !strings.Contains(rec.Body.String(), "SelfPost 9.9.9-test") {
+		t.Errorf("rendered page does not show the version:\n%s", rec.Body.String())
+	}
+}
+
 func TestNavMarksActivePage(t *testing.T) {
 	tmpl, err := loadTemplates()
 	if err != nil {