Owner-only admin page: Reader roster plus Poll Lane status (#102) (#107)

Closes #102.

The only operational surface was /healthz and a fold-out roster inside the owner's own reading page. This adds /admin: an owner-only page carrying the Reader roster and one row per Poll Lane.

- **Poller seam.** `latest.Poller` records each Lane's last pass (`Site`, `Due`, `Checked`, `LastRun`, `Gap`, `Clamped`, `Browser`) and answers `LaneStatus()`; the page reads that snapshot, never a table. A pass that returns before computing its figures (refusal backoff, sidecar down) carries the previous pass's figures forward rather than recording zeroes, and a Lane that has never reached a pace renders no gap at all. Refusal and sidecar reachability are derived at snapshot time.
- **Owner gate at registration.** Every route reaching past the acting Reader lives in `adminRoutes()` and is wrapped in `requireOwner` when it is registered, so a missing gate is visible in the route list rather than hidden in a handler. `web.AdminPatterns()` is what the gate test walks, so a new route cannot be added without being tested. A non-owner gets 404, never 403.
- **Nil poller is a first-class state.** `main.newRouter` takes the reporter as an interface and converts a nil `*Poller` to a nil interface; no poller and no completed pass both render "No data yet" with the reason spelled out, rather than confident zeroes.
- **Roster moved** off the reading page onto /admin, with the Sighting counters and a confirm-gated `Clear marks` control. #103 fills those counters, so on delivery they read zero for everyone - deliberate ordering.
- **One accent, `--patina`** (verdigris, both colour branches): the far side of the wheel from ember's crimson and clear of the archive blue. Ember still means new chapter only; revocation still wears --danger.

Verification: `go vet ./...` and `go test ./...` green (Docker-backed); admin page screenshotted at 1100px and 390px in both colour schemes. Reviewed on both axes (spec, standards); findings on the accent hue, zero-figure honesty and three tests that could not fail are fixed in 58014eb.
Reviewed-on: #107
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/internal/latest/poller_test.go

@@ -1580,3 +1580,91 @@ func TestRunOnceClampWarningNamesTheSite(t *testing.T) {
 		t.Fatalf("clamp warning = %q, want it to name asura and 3601", got)
 	}
 }
+
+// The owner's admin page (issue #102) reads Lane state out of the poller.
+// Before any pass the snapshot is empty — a restart must render "no data
+// yet", not zeroes — and each pass records what it saw: the frozen clock,
+// the due count and the pace, with refusal backoff derived at snapshot time.
+func TestLaneStatus(t *testing.T) {
+	s, _ := newTestStore(t)
+	now := time.UnixMilli(5_000_000)
+	p := newTestPoller(t, s, &fakeFetcher{body: asuraSeriesFixture, status: 200}, now)
+
+	if st := p.LaneStatus(); len(st.Lanes) != 0 {
+		t.Fatalf("lanes before any pass = %d, want 0 (nothing has run)", len(st.Lanes))
+	} else if st.BrowserConfigured || st.BrowserReachable {
+		t.Fatalf("browser before any pass = configured=%v reachable=%v, want false without a browser fetcher", st.BrowserConfigured, st.BrowserReachable)
+	}
+
+	seedForCheck(t, s, "asura:chronicles", "https://asurascans.com/series/chronicles", 0)
+	// Two refusals put kagane's Lane into backoff; asura sits on its own Lane.
+	browser := &fakeFetcher{status: 403}
+	p.BrowserFetch = browser
+	for i := range 2 {
+		key := fmt.Sprintf("kagane:s%d", i)
+		seedForCheck(t, s, key, "https://kagane.to/series/"+key[7:], 0)
+	}
+	p.runOnce(context.Background())
+
+	st := p.LaneStatus()
+	var asura, kagane LaneState
+	for _, lane := range st.Lanes {
+		switch lane.Site {
+		case "asura":
+			asura = lane
+		case "kagane":
+			kagane = lane
+		}
+	}
+	if st.Lanes[0].Site != "asura" {
+		t.Fatalf("first lane = %q, want asura (snapshot sorted by Site)", st.Lanes[0].Site)
+	}
+	if asura.Site == "" {
+		t.Fatalf("asura missing from snapshot: %+v", st.Lanes)
+	}
+	if !asura.LastRun.Equal(now) {
+		t.Fatalf("asura LastRun = %s, want the frozen clock %s", asura.LastRun, now)
+	}
+	if asura.Due != 1 {
+		t.Fatalf("asura Due = %d, want 1", asura.Due)
+	}
+	if asura.Gap == 0 {
+		t.Fatal("asura Gap = 0, want the Lane's pace")
+	}
+	if asura.Browser || asura.Refusing {
+		t.Fatalf("asura = %+v, want a TLS Lane that is not refusing", asura)
+	}
+	if !kagane.Browser || !kagane.Refusing {
+		t.Fatalf("kagane = %+v, want a browser Lane in refusal backoff", kagane)
+	}
+	if !st.BrowserConfigured || !st.BrowserReachable {
+		t.Fatalf("browser after round = configured=%v reachable=%v, want true/true (sidecar never lost)", st.BrowserConfigured, st.BrowserReachable)
+	}
+	if asura.Checked != 1 {
+		t.Fatalf("asura Checked = %d, want the one Series it read", asura.Checked)
+	}
+
+	// A pass that declines to look (kagane is now in backoff) must not restate
+	// the figures it never gathered as zeroes: the last real pass's due count
+	// and pace stand until a pass replaces them.
+	before := kagane
+	if before.Due == 0 || before.Gap == 0 {
+		t.Fatalf("kagane after its refusing pass = %+v, want the figures that pass gathered", before)
+	}
+	p.runOnce(context.Background())
+	for _, lane := range p.LaneStatus().Lanes {
+		if lane.Site != "kagane" {
+			continue
+		}
+		if lane.Due != before.Due || lane.Gap != before.Gap {
+			t.Fatalf("kagane after a skipped pass = due %d gap %s, want the previous pass's %d / %s",
+				lane.Due, lane.Gap, before.Due, before.Gap)
+		}
+	}
+
+	// A lost sidecar reads as unreachable for the same window the Lanes skip.
+	p.setBrowserDown(now)
+	if st := p.LaneStatus(); !st.BrowserConfigured || st.BrowserReachable {
+		t.Fatalf("browser after loss = configured=%v reachable=%v, want true/false", st.BrowserConfigured, st.BrowserReachable)
+	}
+}