Add group-class scheduling, instructor assignment, and details/invite management

Group classes now carry a specific class time (alongside date and duration)
and an assigned instructor:

- Schema: add `class_time` (TIME) to `us_offerings`; `Offering` gains
  `normalizeTime`/`sessionWindows`. (Rides the pending 1.0.0->1.1.0 dbDelta
  upgrade, so no version bump.)
- Offering form: class-time field, plus a studio-admin instructor picker
  (plain instructors always own their own classes).
- `ClassSlotReconciler`: assigning an instructor clears their open booking
  slots overlapping each session and flags already-booked lessons that clash
  (a booked lesson is never deleted). Uses new
  `AvailabilityRepository::findOverlapping`.
- Front end: `GET /offerings` exposes `instructor_name`; the enrolment page
  shows who teaches each class and when it meets.

Back-office group-class views redesigned:

- Instructor **My Group Classes** and studio-admin **Group Classes** are now
  per-class summaries with enrolment counts, not flat student lists.
- Each links through (`?class_id=<id>`) to a per-class **details page**
  (schedule panel, roster with payment status, and — for invite-only classes
  — the add/make-available/invite-by-email controls). Invite-only membership
  is managed entirely from this page.
- Invite actions are allowed for the class's owning instructor or any
  `view_all_lessons` studio admin, so an owner-operator (studio admin who also
  teaches) can reach every class's roster and invites from the Group Classes
  page.

Tests: composer test (508), composer lint, composer cs all pass.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

tests/Unit/Offering/OfferingControllerTest.php

@@ -5,6 +5,7 @@ namespace Unsupervised\Schedular\Tests\Unit\Offering;
 
 use Brain\Monkey\Functions;
 use Mockery;
+use Unsupervised\Schedular\Offering\ClassSlotReconciler;
 use Unsupervised\Schedular\Offering\Offering;
 use Unsupervised\Schedular\Offering\OfferingController;
 use Unsupervised\Schedular\Offering\OfferingRepository;
@@ -13,6 +14,7 @@ use Unsupervised\Schedular\Tests\Unit\TestCase;
 class OfferingControllerTest extends TestCase
 {
     private OfferingRepository&Mockery\MockInterface $repository;
+    private ClassSlotReconciler&Mockery\MockInterface $reconciler;
     private OfferingController $controller;
 
     protected function setUp(): void
@@ -20,13 +22,16 @@ class OfferingControllerTest extends TestCase
         parent::setUp();
 
         $this->repository = Mockery::mock(OfferingRepository::class);
-        $this->controller = new OfferingController($this->repository);
+        $this->reconciler = Mockery::mock(ClassSlotReconciler::class);
+        $this->reconciler->shouldReceive('reconcile')->andReturn(['removed' => 0, 'conflicts' => []])->byDefault();
+        $this->controller = new OfferingController($this->repository, $this->reconciler);
 
         $_POST = [];
         $_GET  = [];
 
         Functions\when('current_user_can')->justReturn(true);
         Functions\when('get_current_user_id')->justReturn(3);
+        Functions\when('get_users')->justReturn([]);
         Functions\when('check_admin_referer')->justReturn(true);
         Functions\when('admin_url')->justReturn('admin.php?page=us-offerings');
         Functions\when('add_query_arg')->alias(
@@ -70,6 +75,90 @@ class OfferingControllerTest extends TestCase
         $this->render();
     }
 
+    public function testAddGroupClassStoresClassTimeAndReconcilesSlots(): void
+    {
+        $_POST = [
+            'usc_action'  => 'add',
+            'title'       => 'Ballet Beginners',
+            'kind'        => Offering::KIND_GROUP_CLASS,
+            'term_start'  => '2026-09-08',
+            'class_time'  => '16:30',
+            'duration_minutes' => '60',
+        ];
+
+        $this->repository->shouldReceive('insert')->once()->with(Mockery::on(
+            static fn (Offering $o) => '16:30:00' === $o->classTime
+        ))->andReturn(1);
+        $this->repository->shouldReceive('findAll')->andReturn([]);
+
+        // A scheduled class is reconciled against the instructor's availability,
+        // and the resulting notice is surfaced to the admin.
+        $this->reconciler->shouldReceive('reconcile')->once()->with(Mockery::on(
+            static fn (Offering $o) => '16:30:00' === $o->classTime
+        ))->andReturn(['removed' => 2, 'conflicts' => []]);
+
+        $html = $this->render();
+
+        self::assertStringContainsString('2 open booking slots were removed', $html);
+    }
+
+    public function testGarbageClassTimeIsRejected(): void
+    {
+        $_POST = [
+            'usc_action' => 'add',
+            'title'      => 'Choir',
+            'kind'       => Offering::KIND_GROUP_CLASS,
+            'class_time' => 'not-a-time',
+        ];
+
+        $this->repository->shouldReceive('insert')->once()->with(Mockery::on(
+            static fn (Offering $o) => null === $o->classTime
+        ))->andReturn(1);
+        $this->repository->shouldReceive('findAll')->andReturn([]);
+
+        $this->render();
+    }
+
+    public function testStudioAdminAssignsClassToChosenInstructor(): void
+    {
+        $_POST = [
+            'usc_action'          => 'add',
+            'title'               => 'Choir',
+            'kind'                => Offering::KIND_GROUP_CLASS,
+            'class_instructor_id' => '7',
+        ];
+
+        $this->repository->shouldReceive('insert')->once()->with(Mockery::on(
+            static fn (Offering $o) => 7 === $o->instructorId
+        ))->andReturn(1);
+        $this->repository->shouldReceive('findAll')->andReturn([]);
+
+        $this->render();
+    }
+
+    public function testInstructorCannotReassignClassToAnotherInstructor(): void
+    {
+        // A plain instructor (no manage_instructors) — the posted instructor id
+        // must be ignored so the class stays theirs.
+        Functions\when('current_user_can')->alias(
+            static fn (string $cap) => 'manage_instructors' !== $cap
+        );
+
+        $_POST = [
+            'usc_action'          => 'add',
+            'title'               => 'Choir',
+            'kind'                => Offering::KIND_GROUP_CLASS,
+            'class_instructor_id' => '7',
+        ];
+
+        $this->repository->shouldReceive('insert')->once()->with(Mockery::on(
+            static fn (Offering $o) => 3 === $o->instructorId
+        ))->andReturn(1);
+        $this->repository->shouldReceive('findAll')->andReturn([]);
+
+        $this->render();
+    }
+
     public function testAddInviteOnlyGroupClassStoresInviteOnlyAccess(): void
     {
         $_POST = [