Readiness, Electrum status, audit browsing and logs (B-92, API-37, API-46, API-47, AUD-34, AUD-41, ARC-02, ARC-09, ARC-61, ELC-29, SEC-48)

- GET /health/ready (Electrum connected, header < 1800s, scheduler heartbeat < 30s) is the
  container healthcheck; the scheduler beats on every tick and draw-wait iteration
- GET /admin/electrum and an Electrum indicator in /admin (server, header age, last rotation)
- GET /admin/audit-log: before_id, event_type, round_id, user_id, from, to; the panel gets filters
- registration writes user_registered in its transaction
- the app's own logs also go to stdout; uvicorn trusts X-Forwarded-For from Caddy's fixed
  address only, so the access log shows the client's IP

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/static/admin.html

@@ -37,6 +37,7 @@
       <span id="chain-status-label">Connessione…</span>
     </span>
     <span class="chain-block mono" id="chain-block">Blocco —</span>
+    <span class="chain-block mono" id="electrum-status">Electrum —</span>
     <button class="secondary" style="margin:8px 0 8px 14px" onclick="adminLogout()">Esci</button>
   </nav>
 
@@ -153,7 +154,17 @@
 
     <div class="view" id="view-audit">
       <h2 class="section-title">Audit log</h2>
-      <p class="hint">Ultimi eventi registrati dal sistema (config, bet, payout, accessi a chiavi private, ecc.).</p>
+      <p class="hint">Eventi registrati dal sistema (config, bet, payout, accessi a chiavi private, ecc.), dal più recente. I filtri si combinano; "Carica altri" prosegue dall'ultimo evento mostrato.</p>
+      <div class="card">
+        <div class="row-between" style="flex-wrap:wrap;gap:8px">
+          <input id="audit-f-type" placeholder="Tipo (es. payout_failed)" style="width:200px" />
+          <input id="audit-f-round" placeholder="Round" inputmode="numeric" style="width:90px" />
+          <input id="audit-f-user" placeholder="Utente" inputmode="numeric" style="width:90px" />
+          <input id="audit-f-from" type="datetime-local" title="Da" />
+          <input id="audit-f-to" type="datetime-local" title="A" />
+          <button class="secondary" style="width:auto;margin-top:0" onclick="loadAuditLog()">Filtra</button>
+        </div>
+      </div>
 
       <div class="card">
         <div class="table-wrap">
@@ -164,6 +175,7 @@
             <tbody id="audit-tbody"></tbody>
           </table>
         </div>
+        <button id="audit-more" class="secondary hidden" style="width:auto" onclick="loadAuditLog(true)">Carica altri</button>
       </div>
     </div>