Upgrade PHPStan to 2.x and raise analysis level from 6 to 10

- Bump phpstan/phpstan ^2.0 and szepeviktor/phpstan-wordpress ^2.0
- Move the analysis level into phpstan.neon (single source) and raise it to 10
- Add Val, a runtime coercion helper that narrows untyped WordPress boundary
  values (wpdb rows, REST params, superglobals, options) with explicit checks
  instead of blind casts, plus unit tests
- Type value-object fromRow() params as stdClass (what wpdb returns) and map
  columns through Val so unexpected shapes degrade safely
- Use %i identifier placeholders for table names in all wpdb::prepare() calls
  so every query string is a literal and identifiers are escaped by WordPress;
  raises the minimum WordPress version to 6.2 where %i was introduced
- Guard wpdb::prepare() null result before wpdb::query() in updateTax()
- Fix nullable get_permalink()/strtotime() handling, list types at REST and
  capability call sites, dead null-coalescing on checked superglobals, and
  narrow get_users() results before mapping
- Register Val method names with the ValidatedSanitizedInput sniff so it
  validates the real sanitizer around each superglobal read
- Update repository unit tests for the %i placeholder arguments

Co-Authored-By: Claude Fable 5 <[email protected]>

src/Payment/PaymentController.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 namespace Unsupervised\Schedular\Payment;
 
 use Unsupervised\Schedular\Auth\RoleManager;
+use Unsupervised\Schedular\Val;
 
 class PaymentController {
 
@@ -19,10 +20,10 @@ class PaymentController {
 
 		if ( isset( $_POST['usc_action'] ) && check_admin_referer( 'usc_payment_action' ) ) {
 			// phpcs:ignore WordPress.Security.NonceVerification.Missing -- nonce checked above.
-			if ( 'mark_paid' === sanitize_key( wp_unslash( $_POST['usc_action'] ?? '' ) ) ) {
+			if ( 'mark_paid' === sanitize_key( Val::string( wp_unslash( $_POST['usc_action'] ) ) ) ) {
 				// phpcs:disable WordPress.Security.NonceVerification.Missing
-				$paymentId = absint( $_POST['payment_id'] ?? 0 );
-				$email     = sanitize_email( wp_unslash( $_POST['etransfer_email'] ?? '' ) );
+				$paymentId = absint( Val::int( $_POST['payment_id'] ?? 0 ) );
+				$email     = sanitize_email( Val::string( wp_unslash( $_POST['etransfer_email'] ?? '' ) ) );
 				// phpcs:enable WordPress.Security.NonceVerification.Missing
 				if ( $paymentId > 0 ) {
 					// Record the destination it was actually sent to before confirming.