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>

modules/helpdesk/lib/Module/Helpdesk/Service/RiskRadarService.php

@@ -332,7 +332,7 @@ final class RiskRadarService
         $days = isset($m[1]) && $m[1] !== '' ? (int) $m[1] : 0;
         $hours = isset($m[2]) && $m[2] !== '' ? (int) $m[2] : 0;
         $minutes = isset($m[3]) && $m[3] !== '' ? (int) $m[3] : 0;
-        $seconds = isset($m[4]) && $m[4] !== '' ? (int) floor((float) $m[4]) : 0;
+        $seconds = isset($m[4]) ? (int) floor((float) $m[4]) : 0;
 
         return ($days * 86400) + ($hours * 3600) + ($minutes * 60) + $seconds;
     }
@@ -355,7 +355,7 @@ final class RiskRadarService
     private static function resolveActivityTimestamp(array $ticket): ?int
     {
         $lastActivity = trim((string) ($ticket['Last_Activity_Date'] ?? ''));
-        if ($lastActivity !== '' && !str_starts_with($lastActivity, '0001-01-01')) {
+        if (!str_starts_with($lastActivity, '0001-01-01')) {
             $ts = strtotime($lastActivity);
             if (is_int($ts)) {
                 return $ts;