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/internal/web/web.go

@@ -50,9 +50,14 @@ type Handler struct {
 	// httpClient is the plain stdlib client that talks to Discord. It is not
 	// an injected interface: tests point APIBase at a stub server instead.
 	httpClient *http.Client
-	// lanes is the Poll Lane snapshot source the administrative page reads.
-	// Nil is a running deployment with no poller, not a bug.
-	lanes LaneReporter
+	// pollerEnabled reports whether latest-chapter polling is switched on in
+	// this deployment (LATEST_CHAPTER_POLL_ENABLED) and browserConfigured
+	// whether a browser sidecar is configured (BROWSER_WS_URL set). Both are
+	// deployment facts resolved by the composition root; the Lanes page (issue
+	// #145) reports them from config and derives reachability from the pass
+	// log rather than from whether a poller goroutine happened to start.
+	pollerEnabled     bool
+	browserConfigured bool
 }
 
 // listView is what every list-rendering template receives.
@@ -110,9 +115,11 @@ type loginView struct {
 // New parses every template up front so a broken one kills the process at
 // startup rather than the first request that touches it.
 //
-// lanes is the administrative page's window onto the running Poller; nil means
-// nothing is polling, which the page reports rather than hides.
-func New(s *store.Store, discord DiscordConfig, tokenKey []byte, mangaPath, novelPath string, lanes LaneReporter) (*Handler, error) {
+// pollerEnabled and browserConfigured are deployment facts the composition
+// root resolves from LATEST_CHAPTER_POLL_ENABLED and BROWSER_WS_URL: the Lanes
+// page (issue #145) reports them and derives browser reachability from the
+// pass log, so no running poller is wired through here at all.
+func New(s *store.Store, discord DiscordConfig, tokenKey []byte, mangaPath, novelPath string, pollerEnabled, browserConfigured bool) (*Handler, error) {
 	tmpl, err := template.ParseFS(templateFS, "templates/*.html")
 	if err != nil {
 		return nil, err
@@ -127,7 +134,8 @@ func New(s *store.Store, discord DiscordConfig, tokenKey []byte, mangaPath, nove
 		states:              newOAuthStates(),
 		limiter:             session.NewLoginLimiter(),
 		httpClient:          &http.Client{Timeout: discordTimeout},
-		lanes:               lanes,
+		pollerEnabled:       pollerEnabled,
+		browserConfigured:   browserConfigured,
 	}, nil
 }