feat: paginated ranking scrape with lazy page fetching

- ScrapeRanking now accepts a maxPages int parameter (0 = all pages).
  Each page is fetched strictly sequentially; the next page is only
  requested after every entry from the current page has been sent,
  so there is no pre-fetching or look-ahead.
  Pagination stops automatically when no next-page link is present
  or when the rank-novels container is absent/empty.

- The ranking URL pattern follows the existing catalogue convention:
  /ranking?page=N (next-page link detection as the stop condition).

- Server: handleRankingRefresh reads an optional 'pages' form field
  and passes it to ScrapeRanking. Timeout scales at 90 s/page.

- UI: Refresh Rankings button is now a small form with a numeric
  'Pages' input (default 1), letting the user choose how many pages
  to pull in one refresh without touching the server config.

scraper/internal/server/ui.go

@@ -222,13 +222,21 @@ const rankingTmpl = `
          class="text-sm px-3 py-1.5 rounded-lg bg-zinc-700 hover:bg-zinc-600 text-white inline-flex items-center gap-1">
         View Markdown
       </a>
-      <button
+      <form
         hx-post="/ranking/refresh"
         hx-target="#ranking-refresh-status"
         hx-swap="innerHTML"
-        class="text-sm px-3 py-1.5 rounded-lg bg-amber-700 hover:bg-amber-600 text-white inline-flex items-center gap-2">
-        Refresh Rankings
-      </button>
+        class="flex items-center gap-2">
+        <label class="flex items-center gap-1.5">
+          <span class="text-xs text-zinc-400 whitespace-nowrap">Pages</span>
+          <input type="number" name="pages" value="1" min="1"
+                 class="w-16 rounded-lg bg-zinc-800 border border-zinc-700 px-2 py-1 text-sm text-zinc-100 text-center focus:outline-none focus:border-amber-500 transition-colors" />
+        </label>
+        <button type="submit"
+          class="text-sm px-3 py-1.5 rounded-lg bg-amber-700 hover:bg-amber-600 text-white inline-flex items-center gap-2">
+          Refresh Rankings
+        </button>
+      </form>
     </div>
   </div>
   <div id="ranking-refresh-status" class="mt-2"></div>
@@ -353,7 +361,18 @@ func (s *Server) handleRanking(w http.ResponseWriter, r *http.Request) {
 // handleRankingRefresh starts an async scrape of novelfire.net/ranking and
 // immediately returns a polling badge. The browser polls /ui/ranking/status
 // until the job finishes, then follows an HX-Redirect back to /ranking.
+//
+// Accepts an optional form field "pages" (integer ≥ 1). 0 or absent means
+// fetch all pages; otherwise at most that many pages are scraped.
 func (s *Server) handleRankingRefresh(w http.ResponseWriter, r *http.Request) {
+	_ = r.ParseForm()
+	maxPages := 0
+	if p := strings.TrimSpace(r.FormValue("pages")); p != "" {
+		if n, err := strconv.Atoi(p); err == nil && n > 0 {
+			maxPages = n
+		}
+	}
+
 	s.mu.Lock()
 	if s.rankingRunning {
 		s.mu.Unlock()
@@ -370,10 +389,15 @@ func (s *Server) handleRankingRefresh(w http.ResponseWriter, r *http.Request) {
 			s.mu.Unlock()
 		}()
 
-		ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+		// Allow ~90 s per page; minimum 120 s for a single page.
+		timeout := 120 * time.Second
+		if maxPages > 1 {
+			timeout = time.Duration(maxPages) * 90 * time.Second
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
 		defer cancel()
 
-		rankingCh, errCh := s.novel.ScrapeRanking(ctx)
+		rankingCh, errCh := s.novel.ScrapeRanking(ctx, maxPages)
 
 		var rankingItems []writer.RankingItem
 		for {