P2R-02 follow-up: clickable rows on Sources/Schedules + cron-preset tooltips

Aligns Sources and Schedules tab rows with the dashboard's row-click
UX: whole-row click navigates to the row's edit page (mirroring
.host-row.clickable). Drops the redundant Edit buttons; Run-now and
Delete remain in .row-action cells that sit above the row-link
overlay via z-index.

Schedule edit form's cron preset chips now carry human-readable
title= tooltips ("Every day at 03:00", "Every Sunday at 03:00", etc).

tasks.md gets a binding row-design rule covering all current and
future list-row templates, and the P2R-02 entry is split into the
six slices already agreed with the operator (slices 1–3 marked
done, 4 next).

internal/server/http/p2r01_test.go

@@ -439,7 +439,10 @@ func TestRunSourceGroupOfflineHost(t *testing.T) {
 		url+"/hosts/"+hostID+"/source-groups/"+gid+"/run", nil)
 	req.AddCookie(cookie)
 	req.Header.Set("Accept", "application/json")
-	res, _ := stdhttp.DefaultClient.Do(req)
+	res, err := stdhttp.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("do: %v", err)
+	}
 	defer res.Body.Close()
 	if res.StatusCode != stdhttp.StatusServiceUnavailable {
 		t.Errorf("offline: want 503, got %d", res.StatusCode)
@@ -456,7 +459,10 @@ func TestRunSourceGroupUnknownGroup(t *testing.T) {
 		url+"/hosts/"+hostID+"/source-groups/no-such-gid/run", nil)
 	req.AddCookie(cookie)
 	req.Header.Set("Accept", "application/json")
-	res, _ := stdhttp.DefaultClient.Do(req)
+	res, err := stdhttp.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("do: %v", err)
+	}
 	defer res.Body.Close()
 	if res.StatusCode != stdhttp.StatusNotFound {
 		t.Errorf("unknown group: want 404, got %d", res.StatusCode)