fix: show most recent dates first in return rate and retention tables

- Reverse new player return rate table (most recent day at top)
- Reverse 7- and 30-day retention tables (most recent cohort at top)
- Rename "Day Rate" column to "Return Rate"
- Clarify "Last 14 Days" heading to "Last 14 Days — Completions"

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

src/routes/global/+page.svelte

@@ -178,7 +178,7 @@
               <tr class="bg-white/5 text-gray-400 text-xs uppercase tracking-wide">
                 <th class="text-left px-4 py-3">Date</th>
                 <th class="text-right px-4 py-3">New Players</th>
-                <th class="text-right px-4 py-3">Day Rate</th>
+                <th class="text-right px-4 py-3">Return Rate</th>
                 <th class="text-right px-4 py-3">7d Avg</th>
                 <th class="px-4 py-3 w-32"></th>
               </tr>
@@ -208,7 +208,7 @@
     </section>
 
     <section class="mt-8">
-      <h2 class="text-lg font-semibold text-gray-100 mb-4">Last 14 Days</h2>
+      <h2 class="text-lg font-semibold text-gray-100 mb-4">Last 14 Days — Completions</h2>
       <div class="overflow-x-auto rounded-xl border border-white/10">
         <table class="w-full text-sm">
           <thead>