refactor(desktop): tighten account dedup, probe scheduling, and session cleanup

- Dedup AI platform accounts by platform ID rather than identity key, preferring higher health rank then newer verified_at
- Clean up session data and health records when duplicate or replaced accounts are removed
- Remove reconcileTrackedAccountRemoteState — no longer optimistically trust remote health state
- Spread initial probes over a random window (5s–3min) to avoid thundering-herd on startup
- Stop scheduling a next probe after an account is marked expired
- Update AI platforms stats strip to show authorized/pending instead of configured/authorized

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/desktop-client/src/renderer/views/AiPlatformsView.vue

@@ -45,9 +45,11 @@ function isLocallyAuthorized(account: AccountRow | null): boolean {
 }
 
 const overview = computed(() => ({
-  configuredPlatforms: desktopMonitoringMediaCatalog.length,
   authorized: platformCards.value.filter((platform) => isLocallyAuthorized(platform.account))
     .length,
+  pending: platformCards.value.filter(
+    (platform) => platform.account && !isLocallyAuthorized(platform.account),
+  ).length,
   onlineClients: snapshot.value?.summary.onlineClients ?? 0,
 }))
 
@@ -259,12 +261,12 @@ async function unbindPlatform(account: AccountRow) {
 
       <div class="stats-strip">
         <div class="stat-card">
-          <div class="stat-label">支持平台</div>
-          <div class="stat-value">{{ overview.configuredPlatforms }}</div>
+          <div class="stat-label">已授权</div>
+          <div class="stat-value">{{ overview.authorized }}</div>
         </div>
         <div class="stat-card">
-          <div class="stat-label">授权正常</div>
-          <div class="stat-value">{{ overview.authorized }}</div>
+          <div class="stat-label">待处理</div>
+          <div class="stat-value">{{ overview.pending }}</div>
         </div>
         <div class="stat-card">
           <div class="stat-label">在线客户端</div>