Add Top Movers screener (mid-cap+, options-tradable)

New /movers page surfaces Yahoo Finance's predefined screeners
(day_gainers, day_losers, most_actives, most_shorted_stocks)
filtered to common equities with market cap >= $2B, so every
listed name has a deep options chain. Per-row actions jump
straight into Chain / Vol Surface / IV Spike Scanner, or pin
the symbol to the Tracker watchlist.

- datafetch.ts: fetchMovers(category, count) using yf.screener,
  post-filtered to quoteType=EQUITY and marketCap >= $2B
- options.ts: GET /api/movers?category=&count=
- movers.html: Tabler page with 4-tab segmented control, sortable
  table, summary cards, volume-vs-avg ratio highlighting hot names
- All page sidebars: insert "Movers" link between Vol Surface
  and Scanner

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/tracker.html

@@ -152,6 +152,18 @@
               </a>
             </li>
 
+            <li class="nav-item">
+              <a class="nav-link" href="movers.html">
+                <span class="nav-link-icon d-md-none d-lg-inline-block">
+                  <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
+                    <path stroke="none" d="M0 0h24v24H0z" fill="none"/>
+                    <path d="M3 17l6 -6l4 4l8 -8"/>
+                    <path d="M14 7l7 0l0 7"/>
+                  </svg>
+                </span>
+                <span class="nav-link-title">Movers</span>
+              </a>
+            </li>
             <li class="nav-item">
               <a class="nav-link" href="scanner.html">
                 <span class="nav-link-icon d-md-none d-lg-inline-block">