T16: saldo liquid akun BP di dashboard (API databisnis + cache TTL)

Sel stat SALDO LIQUID menampilkan account.core_liquid_balance dari
GET {DATABISNIS_API}/v2/state/get_account. Cache in-memory per worker
selama DASH_LIQUID_TTL (60s); gagal fetch → nilai lama (atau '—' bila
belum pernah sukses) + cooldown supaya API tak dipukul berulang. Stats
grid 4 kolom desktop, 2x2 tablet. Oracle + smoke lolos.

templates/index.html

@@ -36,6 +36,10 @@
         <span class="cell-value">{{ top_staked|vex }}</span>
         <span class="cell-label">STAKE TERTINGGI</span>
       </div>
+      <div class="spec-cell">
+        <span class="cell-value">{{ liquid_vex|vex if liquid_vex is not none else '—' }}</span>
+        <span class="cell-label">SALDO LIQUID</span>
+      </div>
     </section>
 
     <form class="search" method="get" action="{{ url_for('index') }}">