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 <noreply@anthropic.com>

src/GroupClass/Enrollment.php

@@ -3,6 +3,8 @@ declare(strict_types=1);
 
 namespace Unsupervised\Schedular\GroupClass;
 
+use Unsupervised\Schedular\Val;
+
 class Enrollment {
 
 	public const STATUS_ACTIVE    = 'active';
@@ -25,14 +27,14 @@ class Enrollment {
 		public readonly ?int $id = null,
 	) {}
 
-	public static function fromRow( object $row ): self {
+	public static function fromRow( \stdClass $row ): self {
 		return new self(
-			offeringId:   (int) $row->offering_id,
-			studentId:    (int) $row->student_id,
-			instructorId: (int) $row->instructor_id,
-			status:       $row->status,
-			paymentId:    null !== $row->payment_id ? (int) $row->payment_id : null,
-			id:           (int) $row->id,
+			offeringId:   Val::int( $row->offering_id ),
+			studentId:    Val::int( $row->student_id ),
+			instructorId: Val::int( $row->instructor_id ),
+			status:       Val::string( $row->status ),
+			paymentId:    Val::intOrNull( $row->payment_id ),
+			id:           Val::int( $row->id ),
 		);
 	}