feat(web,store,latest): forced poll — Check now stamps a Series for the next Lane pass (#146)

The control writes series.force_poll_at (column landed in migration 0014)
and never commands the poller: pending is derived as force_poll_at >
latest_checked_at and self-clears because the check stamp is written before
the fetch. The due query's forced flag overrides the rest cutoff, the
Sighting-deferral and finished-only clauses, jumps the queue, and wakes a
sleeping browser Lane; it never overrides an empty series_url, the Bookmarks
join, the refusal backoff, the sidecar-down skip or the Lane gap.

ADRs: 0013-commands-through-the-database.

backend/internal/web/admin_series_detail.go

@@ -31,6 +31,15 @@ type seriesDetailView struct {
 	NoCover        bool
 	Orphan         bool // no Reader holds the Series
 	SightingRaised bool // a Reader's Sighting set the Latest Chapter
+
+	// Poll is the Check now control and the pending marker (issue #146): the
+	// same derivation and visibility as the list row. CanPoll is false on a
+	// Series with no page to fetch and on an orphan; Pending is derived —
+	// the request stamp is newer than the check stamp — and Requested is its
+	// ageing label.
+	CanPoll   bool
+	Pending   bool
+	Requested string
 }
 
 // adminSeriesDetail renders one Series' page, keyed by the composite
@@ -38,35 +47,50 @@ type seriesDetailView struct {
 // the list's own SeriesPage read narrowed to the key's Site: the admin
 // projection is the privacy boundary, and a dedicated single-row read would
 // be a second definition of it.
-// ponytail: a page scan per detail view, one query per page of the Site's
-// rows up to the window total; a keyed read alongside SeriesPage when the
-// library outgrows the page size.
 func (h *Handler) adminSeriesDetail(w http.ResponseWriter, r *http.Request) {
 	site, seriesID, ok := strings.Cut(r.PathValue("key"), ":")
 	if !ok || site == "" || seriesID == "" {
 		http.NotFound(w, r)
 		return
 	}
+	a, found, err := h.adminSeriesByKey(site, seriesID)
+	if err != nil {
+		log.Printf("series detail %s: %v", site+":"+seriesID, err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	if !found {
+		http.NotFound(w, r)
+		return
+	}
+	h.renderAdmin(w, adminView{Page: "series-detail", Detail: h.seriesDetailView(a)})
+}
+
+// adminSeriesByKey reads one Series through the list's own SeriesPage read
+// narrowed to the key's Site: the admin projection is the privacy boundary,
+// and a dedicated single-row read would be a second definition of it. Absence
+// is reported with found=false, never an error.
+// ponytail: a page scan per keyed read, one query per page of the Site's rows
+// up to the window total; a keyed read alongside SeriesPage when the library
+// outgrows the page size.
+func (h *Handler) adminSeriesByKey(site, seriesID string) (store.AdminSeries, bool, error) {
 	seen := 0
 	for page := 1; ; page++ {
 		p, err := h.store.SeriesPage(store.SeriesFilter{Site: site, Page: page})
 		if err != nil {
-			log.Printf("series detail %s: %v", site+":"+seriesID, err)
-			http.Error(w, "internal error", http.StatusInternalServerError)
-			return
+			return store.AdminSeries{}, false, err
 		}
 		seen += len(p.Rows)
 		for i := range p.Rows {
 			if p.Rows[i].SeriesID == seriesID {
-				h.renderAdmin(w, adminView{Page: "series-detail", Detail: h.seriesDetailView(p.Rows[i])})
-				return
+				return p.Rows[i], true, nil
 			}
 		}
 		if seen >= p.Total {
 			break
 		}
 	}
-	http.NotFound(w, r)
+	return store.AdminSeries{}, false, nil
 }
 
 // seriesDetailView shapes one AdminSeries row for display: every judgement in
@@ -83,6 +107,11 @@ func (h *Handler) seriesDetailView(a store.AdminSeries) seriesDetailView {
 		NoCover:        a.CoverAddress == "",
 		Orphan:         a.ReaderCount == 0,
 		SightingRaised: a.RaisedByReader,
+		CanPoll:        a.SeriesURL != "" && a.ReaderCount > 0,
+	}
+	if a.ForcePollAt > a.LatestCheckedAt {
+		v.Pending = true
+		v.Requested = requestedAge(time.Now(), a.ForcePollAt)
 	}
 	if a.LatestChapterNum == nil {
 		v.Chapter = "—"