fix(capacity): stabilize PTO flows and calendar consistency

Make PTO creation immediately approved, add PTO deletion, and ensure cache invalidation updates individual/team/revenue capacity consistently.

Harden holiday duplicate handling (422), support PTO-day availability overrides without disabling edits, and align tests plus OpenSpec artifacts with the new behavior.

backend/tests/Unit/Resources/PtoResourceTest.php

@@ -19,7 +19,7 @@ test('pto resource returns wrapped data with team member', function () {
         'start_date' => '2026-02-10',
         'end_date' => '2026-02-12',
         'reason' => 'Travel',
-        'status' => 'pending',
+        'status' => 'approved',
     ]);
     $pto->load('teamMember');