Fix CSRF exemption and array-input crash on revocation/introspection

An Opus code review of the branch caught two real bugs the test suite
structurally couldn't see:

- /revocation and /introspect were never added to bootstrap/app.php's
  CSRF except list, so both were fully broken (403) for any real
  external client, despite every feature test passing — CSRF
  verification is short-circuited entirely while running tests.
  Verified live against the running app before and after the fix, and
  added a regression test that asserts against the actual configured
  exemptions rather than relying on request-time behavior that tests
  can't exercise.

- An array-shaped `token` param (e.g. token[]=a&token[]=b) crashed
  both endpoints with a 500, since this app promotes PHP warnings
  ("Array to string conversion") to exceptions. Fixed at the shared
  root, MicropubToken::findActive(), which also closes the same latent
  hole in VerifyMicropubToken's access_token param that predates this
  branch. Verified live and covered with regression tests.

Also applied the review's lower-severity findings: added the missing
introspection_endpoint Link header and metadata test assertions,
removed the now-dead is_string($scopes) array branch in the Micropub
handlers and media controller (scope is unconditionally a string from
the DB now, this guarded against a JWT-array-claim shape that can no
longer occur), dropped a redundant #[Table] model attribute, sized
token_hash to its actual 64-char length, and removed a one-off inline
style in the admin view.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014625MfkGZ7GVdbqKme4a8L

tests/Feature/CsrfExemptionsTest.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Feature;
+
+use Illuminate\Foundation\Http\Middleware\PreventRequestForgery;
+use PHPUnit\Framework\Attributes\Test;
+use Tests\TestCase;
+
+class CsrfExemptionsTest extends TestCase
+{
+    /**
+     * CSRF verification is short-circuited entirely while running the test
+     * suite (see PreventRequestForgery::runningUnitTests()), so a normal
+     * feature test hitting these routes would pass even if they were never
+     * added to bootstrap/app.php's except list. Assert against the actual
+     * configured exemptions instead.
+     */
+    #[Test]
+    public function external_api_endpoints_are_exempt_from_csrf_verification(): void
+    {
+        $exemptions = $this->app->make(PreventRequestForgery::class)->getExcludedPaths();
+
+        foreach (['auth', 'token', 'revocation', 'introspect', 'api/post', 'api/media', 'micropub/places', 'webmention'] as $path) {
+            $this->assertContains($path, $exemptions);
+        }
+    }
+}