dashboard: queued reminders surface

new 'qu3u3d r3m1nd3rs' section between approvals and operator
inbox. lists every pending reminder with agent, due-relative
timestamp, body, payload path (path-linkified), and a cancel
button. drives off a new /api/reminders endpoint and a
POST /cancel-reminder/{id} that hard-deletes the row.

failure surface (last_error / attempt_count + retry) deferred —
needs a sqlite migration; tracked in TODO.md.

hive-c0re/assets/index.html

@@ -45,6 +45,13 @@
     <p class="meta">loading…</p>
   </div>
 
+  <h2>◆ QU3U3D R3M1ND3RS ◆</h2>
+  <div class="divider">══════════════════════════════════════════════════════════════</div>
+  <p class="meta">reminders agents have queued for themselves but not yet delivered. cancel to drop a stuck or unwanted entry.</p>
+  <div id="reminders-section">
+    <p class="meta">loading…</p>
+  </div>
+
   <h2>◆ P3NDING APPR0VALS ◆</h2>
   <div class="divider">══════════════════════════════════════════════════════════════</div>
   <div id="approvals-section">