feat: extract MediaController, wire into Dispatcher, delete media.php

app/templates/partials/flash-messages.php

@@ -0,0 +1,21 @@
+<?php
+/**
+ * Shared flash-message partial for the admin section.
+ *
+ * Consumes all flash variants via App::consumeFlash(), then renders toast markup.
+ * Toast JS in the admin footer auto-removes them after 4 seconds.
+ *
+ * Usage: include once per request in the admin footer.
+ */
+$_flash = App::consumeFlash();
+?>
+<?php if ($_flash['error'] || $_flash['success']): ?>
+<div id="admin-toasts" style="display:none">
+    <?php if ($_flash['error']): ?>
+    <div class="toast" role="alert" data-type="error">⚠ <?= htmlspecialchars($_flash['error']) ?></div>
+    <?php endif; ?>
+    <?php if ($_flash['success']): ?>
+    <div class="toast" role="status" data-type="success">✓ <?= htmlspecialchars($_flash['success']) ?></div>
+    <?php endif; ?>
+</div>
+<?php endif; ?>