refactor: fix all 105 PHPStan 2 strict type findings across core and modules

Resolve all non-false-positive PHPStan 2 findings, reducing the baseline
from 486 to 382 entries (only unused-public false positives remain).

Categories fixed:
- Remove 39 redundant type checks (is_string, is_array, is_object, method_exists)
- Remove 12 no-op array_values() on already-sequential lists
- Simplify 13 null-coalesce on guaranteed offsets
- Remove 8 always-true instanceof checks
- Replace 12 redundant test assertions (assertTrue(true) → addToAssertionCount)
- Simplify 6 unnecessary nullsafe operators (?-> → ->)
- Fix 6 always-true !== '' comparisons
- Fix remaining: unset.offset, return.unusedType, staticMethod narrowing

53 files changed across core/, modules/, pages/, and tests/.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/Console/Runner/Doctor/DoctorRunner.php

@@ -4,7 +4,6 @@ declare(strict_types=1);
 
 namespace MintyPHP\Console\Runner\Doctor;
 
-use MintyPHP\App\AppContainer;
 use MintyPHP\App\Bootstrap\EnvValidator;
 use MintyPHP\Console\Support\CliAppBootstrap;
 use MintyPHP\DB;
@@ -22,8 +21,7 @@ final class DoctorRunner implements DoctorRunnerInterface
         error_reporting(E_ALL & ~E_DEPRECATED & ~E_USER_DEPRECATED);
         ini_set('display_errors', '0');
 
-        /** @var AppContainer $container */
-        $container = CliAppBootstrap::bootstrap('cli', 'bin/console doctor');
+        CliAppBootstrap::bootstrap('cli', 'bin/console doctor');
         $startedAt = microtime(true);
 
         $results = [];
@@ -71,14 +69,7 @@ final class DoctorRunner implements DoctorRunnerInterface
             ];
         });
 
-        $runCheck('App container bootstrap', static function () use ($container): array {
-            if (!$container instanceof AppContainer) {
-                return [
-                    'status' => 'fail',
-                    'message' => 'registerContainer.php did not return AppContainer',
-                ];
-            }
-
+        $runCheck('App container bootstrap', static function (): array {
             app(AuthService::class);
             app(AuthorizationService::class);
             app(UiAccessService::class);