chore: remove unused match-stub and upload-result view templates

Neither src/Views/match-stub.php nor src/Views/upload-result.php is
referenced by any handler or route in Plan 3b:

- match-stub is the Plan 4 battle-interface placeholder; Plan 3b does
  not register a /match route.
- upload-result is the iframe-style post-upload response; Plan 3b
  returns JSON from POST /assets/upload and Plan 3c will wire the
  client-side upload form.

Both files were over-eager scaffolding from Task 3 (6a0b147). Drop
them in a follow-up commit rather than amend the shared Task 3 commit.

src/Views/match-stub.php

@@ -1,28 +0,0 @@
-<?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');

src/Views/upload-result.php

@@ -1,26 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use BattleForge\Http\Escape;
-
-/**
- * @var string $csrf  Provided by the front controller.
- * @var string $url   The uploaded image's URL, written into the parent form's hidden field.
- */
-$e = static fn (string $v): string => Escape::html($v);
-$json = json_encode(['url' => $url], JSON_THROW_ON_ERROR);
-?><?php
-render_layout(static function () use ($e, $url, $json): void {
-    ?>
-    <p>Uploaded: <code><?= $e($url) ?></code></p>
-    <script>
-    (function () {
-        var data = <?= $json /* trusted raw JSON; $url was validated server-side */ ?>;
-        if (window.parent && window.parent !== window) {
-            window.parent.postMessage(Object.assign({type: 'bf-upload'}, data), '*');
-        }
-    })();
-    </script>
-    <?php
-}, $csrf, 'Upload complete');