feat: add chat log admin management and refactor admin panel to lazy-load tab content

frontend/admin/system.html

@@ -0,0 +1,54 @@
+<h1>System Configuration</h1>
+<div class="panel-card split-grid">
+    <section>
+        <h2>Redis Stats</h2>
+        <dl class="kv-list">
+            <div>
+                <dt>Memory Used</dt>
+                <dd id="system-redis-memory">loading...</dd>
+            </div>
+            <div>
+                <dt>Connected Clients</dt>
+                <dd id="system-redis-clients">0</dd>
+            </div>
+            <div>
+                <dt>Redis Enabled</dt>
+                <dd id="system-redis-enabled">no</dd>
+            </div>
+        </dl>
+    </section>
+    <section>
+        <h2>Storage</h2>
+        <dl class="kv-list">
+            <div>
+                <dt>Database Driver</dt>
+                <dd id="system-db-driver">loading...</dd>
+            </div>
+            <div>
+                <dt>Stored Messages</dt>
+                <dd id="system-stored-messages">0</dd>
+            </div>
+            <div>
+                <dt>Last Refresh</dt>
+                <dd id="system-generated-at">loading...</dd>
+            </div>
+            <div>
+                <dt>Playlist Path</dt>
+                <dd id="system-playlist-path">loading...</dd>
+            </div>
+            <div>
+                <dt>Playlist Present</dt>
+                <dd id="system-playlist-present">no</dd>
+            </div>
+        </dl>
+    </section>
+</div>
+
+<div class="panel-card">
+    <div class="panel-header-row">
+        <h2>Service Health</h2>
+        <button id="reload-system-btn" type="button" class="btn btn-secondary">Reload health</button>
+    </div>
+    <div id="system-services" class="service-list"></div>
+    <p id="system-status" class="status-line" aria-live="polite">Loading system summary...</p>
+</div>