add filtering and sorting features; enhance events and articles pages with URL state persistence

public/admin/pages/events.html

@@ -30,6 +30,22 @@
 
 <main class="content">
 
+  <div class="filters">
+    <label>Keyword <input type="text" id="ef-keyword" placeholder="search title..." /></label>
+    <label>Min articles <input type="text" id="ef-min" placeholder="e.g. 2" style="min-width:90px" /></label>
+    <label>From <input type="date" id="ef-from" /></label>
+    <label>To   <input type="date" id="ef-to" /></label>
+    <label>Sort
+      <select id="ef-sort">
+        <option value="created_desc">Newest first</option>
+        <option value="created_asc">Oldest first</option>
+        <option value="articles_desc">Most articles</option>
+        <option value="articles_asc">Fewest articles</option>
+      </select>
+    </label>
+    <button class="primary" id="eSearchBtn" style="align-self:flex-end">Filter</button>
+  </div>
+
   <div class="table-wrap">
     <table>
       <thead>