feat: add battlefield, match stub, and upload result templates

src/Views/match-stub.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+use BattleForge\Http\Escape;
+
+/**
+ * @var string $csrf        Provided by the front controller.
+ * @var ?string $matchJson  The match:current JSON from localStorage, encoded as a string.
+ *                          Null if no match is in progress.
+ */
+$e = static fn (string $v): string => Escape::html($v);
+$matchInfo = $matchJson !== null ? "Match loaded." : "No match in progress.";
+?><?php
+render_layout(static function () use ($e, $matchInfo, $matchJson): void {
+    ?>
+    <h1>Match</h1>
+    <p><?= $e($matchInfo) ?></p>
+    <?php if ($matchJson !== null) : ?>
+        <details>
+            <summary>Match state (debug)</summary>
+            <pre><?= $e($matchJson) ?></pre>
+        </details>
+    <?php endif; ?>
+    <p>Battle interface coming in Plan 4.</p>
+    <p><a href="/">Back to home</a></p>
+    <?php
+}, $csrf, 'Match');