Offer archive expiry choices on the target forms, show plain units (closes #396)

A database target's archive expiry was typed by hand as never or a raw duration such as 720h, and the target list showed it back raw. Adding or editing a database target now offers the new-webhook page's list of choices (never, 1h, 12h, 24h, 30d, 90d, 365d), defined once and shared by all three forms. The edit form starts on the stored expiry, or on the submitted one after a refused save; a stored value outside the choices is listed under its own value, so saving unchanged keeps it. The target list shows the expiry in plain units: "30 days", "12 hours", "never".

Model: opus-5-5

internal/server/alpine_browser_test.go

@@ -71,6 +71,7 @@ func TestAlpineRunsUnderTheSecurityPolicy(t *testing.T) {
 	// this order. A new check is one more line here.
 	checkAddEntrypoint(ctx, t, page)
 	checkAddEachTargetType(ctx, t, page)
+	checkArchiveExpiry(ctx, t, page)
 	checkRefusedTarget(ctx, t, page)
 	checkTargetDeliveries(ctx, t, page, target.Name,
 		"0 in total, 0 in the last 24 hours",
@@ -421,6 +422,43 @@ func chooseTargetType(ctx context.Context, t *testing.T, targetType string) {
 		"%s: Add still shows while the form is open", targetType)
 }
 
+// checkArchiveExpiry loads a webhook page and checks that the add
+// target form's archive expiry starts on never, that the database
+// target checkAddTarget added with 720h is listed as 30 days, and that
+// its edit form starts on 720h.
+func checkArchiveExpiry(ctx context.Context, t *testing.T, url string) {
+	t.Helper()
+
+	const expiry = `form[action$="/targets"] select[name="expiry"]`
+
+	row := `//span[text()="added-database"]/ancestor::div[@class="p-4"][1]`
+
+	require.NoError(t, chromedp.Run(ctx, loadPage(url)))
+
+	chooseTargetType(ctx, t, "database")
+
+	var start, edited string
+
+	require.NoError(t, chromedp.Run(
+		ctx, chromedp.Value(expiry, &start, chromedp.ByQuery),
+	))
+	assert.Equal(t, "never", start,
+		"the add target form's archive expiry does not start on never")
+
+	assert.True(t, shown(ctx, row+`//span[text()="Archive Expiry:"]`+
+		`/following-sibling::span[text()="30 days"]`),
+		"a database target added with 720h is not listed as 30 days")
+
+	click(ctx, t, row+`//a[text()="Edit"]`)
+	require.NoError(t, chromedp.Run(
+		ctx,
+		chromedp.WaitReady("#expiry", chromedp.ByQuery),
+		chromedp.Value("#expiry", &edited, chromedp.ByQuery),
+	))
+	assert.Equal(t, "720h", edited,
+		"the edit form does not start on the stored archive expiry")
+}
+
 // checkRefusedTarget submits an http target the server refuses, a
 // loopback destination, and checks that the page comes back with the
 // form open on the http fields, the values entered and the reason, and