Give each week its own card in the Tasks tab

A new task sheet arrives roughly weekly, so instead of one table that gets
overwritten, Weekly Tasks is now a running list of per-week cards (starting
with Week of 17-21 Aug 2026) -- add a new card each week rather than
replacing the last one.

index.html

@@ -847,9 +847,11 @@
     </div>
 
     <div id="tab-tasks" class="tab-content">
+      <h2 style="margin: 0 0 6px; font-size: 1.3rem; font-weight: 800; color: #1b3a5c;">Weekly Tasks</h2>
+      <p class="narrative">Peter's weekly task sheet (~/Downloads/Mckinley_Weekly_Task_Plan_*.xlsx) — a new one arrives about once a week; each week gets its own card below, newest first. [Placeholder — add a new card each week rather than overwriting the last one.]</p>
+
       <div class="card">
-        <h2>Weekly Tasks</h2>
-        <p class="narrative">Peter's weekly task sheet (~/Downloads/Mckinley_Weekly_Task_Plan_*.xlsx), one sheet tab per week. [Placeholder — update each week from the latest file.]</p>
+        <h3>Week of 17–21 Aug 2026</h3>
         <table class="crm-detail-table">
           <thead>
             <tr><th>Subtask</th><th>Ask</th><th>KPI</th><th>Status</th></tr>