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/Service/User/UserAccessPdfService.php

@@ -105,19 +105,9 @@ class UserAccessPdfService
     private static function configurePdfOptions(Options $options): void
     {
         // Keep PDF rendering deterministic and avoid remote/network execution.
-        if (method_exists($options, 'setIsRemoteEnabled')) {
-            $options->setIsRemoteEnabled(false);
-        } else {
-            $options->set('isRemoteEnabled', false);
-        }
-        if (method_exists($options, 'setIsPhpEnabled')) {
-            $options->setIsPhpEnabled(false);
-        } else {
-            $options->set('isPhpEnabled', false);
-        }
-        if (method_exists($options, 'setDefaultFont')) {
-            $options->setDefaultFont('DejaVu Sans');
-        }
+        $options->setIsRemoteEnabled(false);
+        $options->setIsPhpEnabled(false);
+        $options->setDefaultFont('DejaVu Sans');
     }
 
     private static function renderTemplate(string $template, array $vars, string $locale): string