Add block-update latency tracking, raw share counters, and shares bar UI

Log ZMQ→mining.notify latency in ckpool (patch 0005), expose a raw
reject counter (patch 0006), and surface both in the dashboard:

- Block latency card shows avg/last ms, wasted work, and block count
- SharesBar component shows session + all-time accepted/rejected with
  a Demon Slayer flame-slash animation on new shares
- Miners card info moved to MinersTable section header
- Latency stats and share counts persist across restarts via kv store
- Removed misleading pool-wide share stats from per-worker/user pages
  (ckpool doesn't expose per-user raw counts)

ui/src/lib/MinersTable.svelte

@@ -96,7 +96,14 @@
 </script>
 
 <section class="card">
-  <h2>Miners</h2>
+  <div class="section-head">
+    <h2>Miners</h2>
+    <span class="head-meta">
+      {rows.filter(r => r.online).length} online ·
+      {rows.length} workers ·
+      {new Set(rows.map(r => r.btcAddress)).size} users
+    </span>
+  </div>
   {#if rows.length === 0}
     <div class="empty">No miners connected.</div>
   {:else}
@@ -165,11 +172,21 @@
 </section>
 
 <style>
+  .section-head {
+    display: flex;
+    align-items: baseline;
+    gap: 0.75em;
+    margin-bottom: 1rem;
+  }
   h2 {
-    margin: 0 0 1rem;
+    margin: 0;
     font-size: 1.05rem;
     font-weight: 600;
   }
+  .head-meta {
+    color: var(--fg-dim);
+    font-size: 0.85em;
+  }
   .table-wrap {
     overflow-x: auto;
   }