fix(security): honour Pods field restrictions (audit M4)

PodsFieldSource maps hidden, read_only, admin_only and
restrict_role/-capability like Pods' own view: hidden -> new status
HIDDEN, read_only -> READONLY, restricted and not permitted -> READONLY
with read_only_restricted, else HIDDEN. HIDDEN fields are not described,
read out, queried or written (they look unknown) but stay in the schema
for the media usage search; write() re-checks before Pods' save().
Required-but-restricted fields no longer block a create. Pods is not
active on DDEV: covered by unit tests with a field-option fixture.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Integrations/WordPress/Schema/FieldValidator.php

@@ -27,7 +27,7 @@ final class FieldValidator
         foreach ($values as $key => $value) {
             $key = (string) $key;
             $field = $definitions[$key] ?? null;
-            if ($field === null) {
+            if ($field === null || $field->status === FieldDefinition::HIDDEN) {
                 $errors[$key] = 'Unbekanntes Feld; verfügbare Felder über lit/content-types (direkt: '
                     . 'lit-content-types) abrufen.';
                 continue;
@@ -55,7 +55,9 @@ final class FieldValidator
         }
 
         foreach ($definitions as $key => $field) {
-            if (! $field->required || isset($errors[$key])) {
+            // A field the user cannot write (readonly, hidden) cannot be required from them either.
+            $writable = in_array($field->status, [FieldDefinition::WRITABLE, FieldDefinition::UNKNOWN], true);
+            if (! $field->required || ! $writable || isset($errors[$key])) {
                 continue;
             }