Spec #136: Finished belongs to the Series — owner-owned poll gate, Lifecycle bucket dropped (#163)

Closes #136.

Spec #136 end to end: `finished` becomes a fact about the Series, written only by the owner, and the reader-facing Lifecycle bucket is gone.

## What landed

- **#157** — `series.finished_at bigint NOT NULL DEFAULT 0` plus the migration whose statement order is load-bearing (seed from the buckets, then flip them); both Lane queries lose the `HAVING COUNT(*) FILTER (WHERE b.status <> 'finished')` clause and gate on `finished_at = 0` instead, with the due-query/eligible-count force asymmetry kept deliberate and commented; `StatusFinished`, its API special-case 400, the web tab and the templates' Finished bucket deleted.
- **#158** — owner Finish control on the Series detail page: confirm-gated finish, instant un-finish, admin accent (never ember, nothing is destroyed), `Store.SetSeriesFinished`, the two routes behind the owner gate, and the state displayed on the list row without offering the control there.
- **#160** — reader side: derived `finished` bool on the flat Bookmark (`s.finished_at > 0`), rendered as a text-only label in both userscripts and on the web card; read-only inbound by omission from `Upsert`'s explicit `series` column list, same mechanism that already protects `cover`.
- **#161** — glossary and the stale Reader-count divergence note catch up.
- **#159** — `finished` joins the admin filter vocabulary (predicate `finished_at > 0`, label `Finished`, own aggregate count, figure last in the stats block as informational); the four clock-driven hygiene predicates (stale, never-checked, no-cover, no-chapter) exclude finished Series while unpollable, orphan and sighting-raised deliberately do not.

## Verification

`go vet ./...` and `go test ./...` green on the merged branch (Docker-backed, throwaway `postgres:17-alpine` per package). Each ticket also passed a two-axis review (spec + standards) on its own branch before merge.

Reviewed-on: #163
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/internal/web/templates/card.html

@@ -1,6 +1,6 @@
 {{define "card"}}
 {{/* One sheet per series. is-new turns the title crimson over an ember rule;
-     is-dim sinks archived and finished rows into italic grey. */}}
+     is-dim sinks archived rows into italic grey. */}}
 <article class="card{{if eq .Status "reading"}}{{if .HasNewChapter}} is-new{{end}}{{else}} is-dim{{end}}"
          id="card-{{.Key}}" data-title="{{.Title}}">
   <div class="row">
@@ -32,9 +32,10 @@
         {{if eq .Status "archived"}}
         <span class="sep">/</span>
         <span class="state">archived</span>
-        {{else if eq .Status "finished"}}
+        {{end}}
+        {{if .Finished}}
         <span class="sep">/</span>
-        <span class="state"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="#i-check"/></svg>finished</span>
+        <span class="state finished">finished</span>
         {{end}}
       </p>
     </div>
@@ -56,7 +57,7 @@
         <svg viewBox="0 0 24 24" aria-hidden="true"><use href="#i-pencil"/></svg>
       </button>
       {{/* Restore is a reversal, so it fires straight away; every move *out* of
-           the list (archive, finish, remove) goes through a confirm row. */}}
+           the list (archive, remove) goes through a confirm row. */}}
       {{if eq .Status "reading"}}
       <button class="lifecycle box" title="Archive" aria-label="Archive"
               aria-expanded="false" aria-controls="confirm-archive-{{.Key}}"
@@ -71,13 +72,6 @@
         <svg viewBox="0 0 24 24" aria-hidden="true"><use href="#i-undo"/></svg>
       </button>
       {{end}}
-      {{if ne .Status "finished"}}
-      <button class="lifecycle finish" title="Mark finished" aria-label="Mark finished"
-              aria-expanded="false" aria-controls="confirm-finish-{{.Key}}"
-              onclick="toggleConfirmRow('{{.Key}}', 'finish')">
-        <svg viewBox="0 0 24 24" aria-hidden="true"><use href="#i-check"/></svg>
-      </button>
-      {{end}}
       <button class="lifecycle remove" title="Remove" aria-label="Remove"
               aria-expanded="false" aria-controls="confirm-remove-{{.Key}}"
               onclick="toggleConfirmRow('{{.Key}}', 'remove')">
@@ -116,18 +110,6 @@
     </div>
   </div>
   {{end}}
-  {{if ne .Status "finished"}}
-  <div class="confirm-row calm" id="confirm-finish-{{.Key}}" role="group" aria-live="polite" hidden>
-    <span>Mark finished?</span>
-    <div>
-      <button class="go"
-              hx-post="/ui/bookmarks/{{.Key}}/status" hx-vals='{"status":"finished"}'
-              hx-target="[id='card-{{.Key}}']" hx-swap="outerHTML"
-              hx-indicator="[id='card-{{.Key}}']" hx-disabled-elt="this">Finish</button>
-      <button type="button" onclick="toggleConfirmRow('{{.Key}}', 'finish')">Cancel</button>
-    </div>
-  </div>
-  {{end}}
   <div class="confirm-row" id="confirm-remove-{{.Key}}" role="group" aria-live="polite" hidden>
     <span>Remove “{{.Title}}”? Chapter progress is lost.</span>
     <div>