feat(web): read admin lanes from the durable pass log, not a poller snapshot (#145)

The Lanes page now projects store.LatestLanePasses and the owner-window
outcomes (store.LanePassOutcomes) into per-Site rows instead of reading an
in-memory Poller snapshot, so a deploy answers the instant the store is up.
Browser configuration is a config fact and reachability is derived from
recent browser-Site passes inside latest.RefuseBackoff.

This atomically deletes the in-memory path in the same commit that makes the
page read the DB: latest/status.go (LaneState, Status, LaneStatus,
recordLaneState) and the web.LaneReporter seam plus fakeLanes are gone, and
latest.refuseBackoff is renamed latest.RefuseBackoff at every callsite.
ownerWindow (#142) is referenced, never declared (contract C2)

backend/cover_test.go

@@ -98,7 +98,7 @@ func TestPublicCoverNeverEchoesNonImage(t *testing.T) {
 	if _, err := db.Exec(`UPDATE covers SET content_type = 'text/html' WHERE address = $1`, address); err != nil {
 		t.Fatalf("poison row: %v", err)
 	}
-	rr := getCover(t, newRouter(st, testConfig(), nil), "/covers/"+address, nil)
+	rr := getCover(t, newRouter(st, testConfig()), "/covers/"+address, nil)
 	if rr.Code == http.StatusOK {
 		t.Fatalf("status = 200, want a refusal for a non-image row (body %q)", rr.Body.String())
 	}