fix(#2650,#2649): drop reminders tab + pending_reminders chip

hive-c0re's broker reminder store and /api/reminders endpoint were
removed in PR #2644 (reminders migrated to in-container sqlite store).
The dashboard had a QU3U3D R3M1ND3RS section on the schedules tab backed
by that endpoint, and a per-agent badge driven by pending_reminders
(always 0 after the migration).

Remove both. Per-agent reminders now surface through get_loose_ends /
the todos pill on the agent page, consistent with the todos migration.

- frontend/packages/dashboard/src/schedules.js: drop refreshReminders,
  renderReminders, applyRemindersChanged; drop appendLinkified import
  (no longer used); update module comment.
- frontend/packages/dashboard/src/tabs.js: drop applyRemindersChanged
  and refreshReminders imports; remove reminders-section from managed
  list; remove refreshReminders call site; drop reminders_changed from
  SSE dispatch; simplify countdown ticker (reminder-due gone).
- frontend/packages/dashboard/src/dashboard.html: remove QU3U3D
  R3M1ND3RS section.
- frontend/packages/dashboard/src/dashboard.css: remove reminder list +
  row CSS.
- frontend/packages/dashboard/src/common.css: remove .badge-reminder.
- frontend/packages/dashboard/src/swarm.js: remove pending_reminders
  from fingerprint key and badge render.

frontend/packages/dashboard/src/swarm.js

@@ -459,7 +459,6 @@ function containerRowFingerprint(c, node, pending, opRunning, selected,
     running: c.running,
     needs_login: c.needs_login,
     needs_update: c.needs_update,
-    pending_reminders: c.pending_reminders,
     active_model: c.active_model,
     port: c.port,
     pending,
@@ -672,14 +671,6 @@ function buildContainerLi(c, node, opts) {
       c.active_model));
   }
 
-  if (c.pending_reminders && c.pending_reminders > 0) {
-    head.append(el('span',
-      {
-        class: 'badge badge-reminder',
-        title: 'pending reminders queued for this agent — see the reminders section to view / cancel',
-      },
-      `⏰ ${c.pending_reminders}`));
-  }
   // Pending questions where this agent is the asker (awaiting an
   // answer) or the target (owes a reply). Derived live from
   // questionsState so the badge updates instantly on QuestionAdded /