web: owner-only /admin with the Reader roster and Poll Lane status (#102)

The only operational surface was /healthz and a fold-out roster inside the
owner's own reading page. This gives the owner a page: two sections of facts on
the same measured sheet, no cards.

- admin.go holds every route that reaches past the acting Reader, listed once
  in adminRoutes() and wrapped in requireOwner at registration - a missing gate
  is visible in the route list rather than hidden inside a handler. A non-owner
  gets 404, the same answer revoke already gave.
- Lane figures arrive through the LaneReporter seam, so the page reads the
  running poller rather than a table. newRouter converts a nil *Poller to a nil
  interface: a typed nil would make the page claim a poller exists.
- The roster moves out of the reading page and gains the Sighting counters, the
  blocked verdict and Clear marks. Clearing restores a privilege, so it is a
  plain ghost button; --danger stays with revocation.
- --patina is the page's one accent, held at the weight of the other action
  accents. Neither --ember (new chapter) nor --danger (destruction) is borrowed
  for system health.

backend/internal/web/static/style.css

@@ -87,6 +87,10 @@
   --moss: #7fae86;         /* finished */
   --clay: #b5906f;         /* set chapter */
   --trash: #977671;        /* remove, resting — icons need 3:1, not 4.5:1 */
+  /* A Lane needing attention: the admin page's only accent, held at the same
+     muted weight as --brass so it never competes with ember. Neither ember
+     (new chapter) nor danger (destruction) may say "system unhealthy". */
+  --patina: #b08a4a;
 
   /* Desktop cell borders for the two coloured action states. */
   --play-hot-line: #3a1d18;
@@ -146,6 +150,7 @@
     --moss: #3d6c46;
     --clay: #7c5533;
     --trash: #8c6558;
+    --patina: #7a5a1e;
 
     --play-hot-line: #f0cfc6;
     --fav-line: #e3d3a4;
@@ -290,9 +295,21 @@ button { cursor: pointer; }
   letter-spacing: .04em;
 }
 
-/* ---- reader roster (owner only): same hairline panel, one row per Reader ---- */
-.readerlist { margin: 0; padding: 0; list-style: none; }
-.readerlist li {
+/* ---- admin page: two sections on the same measured sheet, no cards ----
+   The reading page is a list of series; this is a list of facts. Both are
+   sheets of hairline-separated rows, so the roster keeps the shape it had as
+   a fold-out and the Lane block copies it. */
+.readers, .lanes { margin: 0 20px; padding: 12px 0 16px; border-bottom: 1px solid var(--rule); }
+.readers h2, .lanes h2 {
+  margin: 0;
+  padding: 8px 0;
+  font: 500 10px/1 var(--font-mono);
+  letter-spacing: .2em;
+  text-transform: uppercase;
+  color: var(--mute-2);
+}
+.readerlist, .lanelist { margin: 0; padding: 0; list-style: none; }
+.readerlist li, .lanelist li {
   display: flex;
   align-items: center;
   flex-wrap: wrap;
@@ -300,7 +317,8 @@ button { cursor: pointer; }
   min-height: 44px;
   border-top: 1px solid var(--rule);
 }
-.readerlist form { margin: 0 0 0 auto; }
+.reader-actions { display: flex; gap: 18px; margin-left: auto; }
+.readerlist form { margin: 0; }
 .reader-id {
   font: 500 13px/1.4 var(--font-mono);
   letter-spacing: .04em;
@@ -312,6 +330,30 @@ button { cursor: pointer; }
   text-transform: uppercase;
   color: var(--mute);
 }
+.reader-sightings, .lane-fact {
+  font: 500 10px/1 var(--font-mono);
+  letter-spacing: .14em;
+  text-transform: uppercase;
+  color: var(--mute-2);
+}
+/* Two states the owner is meant to find rather than read for: a Reader whose
+   reports no longer defer a Poll, and a Lane that is not keeping its promise.
+   Both wear --patina — never ember, which means one thing, and never danger,
+   which is destruction. */
+.reader-blocked, .lane-mark {
+  font: 500 10px/1 var(--font-mono);
+  letter-spacing: .14em;
+  text-transform: uppercase;
+  color: var(--patina);
+}
+.lane-site {
+  font: 400 19px/1.2 var(--font-display);
+  color: var(--paper-dim);
+}
+/* The whole row leans patina when the Lane needs attention, so the scan is one
+   pass down the left edge rather than a read of every mark. */
+.lanelist li.attention .lane-site { color: var(--patina); }
+.lane-browser { padding: 12px 0 0; }
 /* Revocation cuts someone off, so it wears --danger. Ember stays reserved for
    the new-chapter signal. */
 .ghost.danger { color: var(--danger); }
@@ -600,6 +642,9 @@ button { cursor: pointer; }
   box-shadow: inset 0 -2px 0 var(--ember);
 }
 .topbar form { margin-left: 18px; }
+/* The admin page's topbar has no switch to fill the middle, so its back link
+   keeps company with Log out at the right edge instead of floating centre. */
+.topbar .back { margin-left: auto; }
 /* At phone width brand + switch + Log out do not fit on one line, so the
    switch takes its own row under the wordmark rather than pushing Log out
    off-screen. */
@@ -609,6 +654,9 @@ button { cursor: pointer; }
   .libswitch { order: 3; margin-left: 0; }
   .libswitch a { flex: 1; text-align: center; padding: 8px 14px; }
   .topbar form { margin-left: 12px; }
+  /* The admin page has no switch to take the second row, so its brand claims
+     the first outright and the back link keeps Log out company below. */
+  .topbar:has(.back) .brand { flex: 1 1 100%; }
 }
 
 /* ---- action strip: full-width on a phone, hairline-divided cells ---- */