Extend availability (durations, weekly recurrence, calendar); price offerings in dollars

Availability (#2):
- us_availability gains offering_id, duration_minutes (default 60), and
  recurrence_group; AvailabilitySlot carries the new fields.
- AvailabilityRepository::createWeeklySeries() generates N weekly rows
  sharing a recurrence_group; findAvailable() filters by offering and
  duration. Date math uses DateTimeImmutable::modify() (the no-debug CI
  regex `dd\(` matches `->add(`).
- REST GET filters by offering_id/duration_minutes; POST accepts
  duration_minutes, offering_id, recurrence (single|weekly) + weeks.
- Admin form adds duration, an offering picker, and one-off/weekly options
  (OfferingRepository wired into AvailabilityController).
- booking.js renders an agenda calendar (slots grouped by day, with
  duration). The richer booking UX lands with the booking-flow work.

Offering price in dollars:
- Switch us_offerings.price_cents (INT) to price DECIMAL(10,2); Offering
  uses float $price. Admin form and REST take dollars.
- Fix a pre-existing misalignment in the Offering insert/update $wpdb
  format arrays (billing_mode/capacity/is_active were mapped to the wrong
  specifiers, which would corrupt values) via a single COLUMN_FORMATS list.

Also bump PHPStan to --memory-limit=1G in the lint script; 128M now
crashes analysis as the codebase has grown.

Refs #2

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/Unit/Availability/AvailabilityRepositoryTest.php

@@ -34,19 +34,50 @@ class AvailabilityRepositoryTest extends TestCase
                 Mockery::on(static function (array $data): bool {
                     return $data['instructor_id'] === 5
                         && $data['start_dt'] === '2026-04-01 09:00:00'
+                        && $data['duration_minutes'] === 30
+                        && $data['offering_id'] === 8
                         && $data['is_booked'] === 0;
                 }),
-                ['%d', '%s', '%s', '%d', '%s']
+                ['%d', '%d', '%s', '%s', '%d', '%d', '%d', '%s']
             );
 
         $this->db->insert_id = 42;
 
-        $slot   = new AvailabilitySlot(5, '2026-04-01 09:00:00', '2026-04-01 10:00:00');
+        $slot   = new AvailabilitySlot(5, '2026-04-01 09:00:00', '2026-04-01 10:00:00', 30, 8);
         $result = $this->repo->insert($slot);
 
         self::assertSame(42, $result);
     }
 
+    public function testCreateWeeklySeriesInsertsWeeklyAndSharesGroup(): void
+    {
+        Functions\when('current_time')->justReturn('2026-04-07 12:00:00');
+
+        $captured = [];
+        $ids      = [10, 11, 12];
+
+        $this->db->shouldReceive('insert')
+            ->times(3)
+            ->andReturnUsing(function (string $table, array $data) use (&$captured, &$ids): void {
+                $captured[] = $data['start_dt'];
+                $this->db->insert_id = array_shift($ids);
+            });
+
+        // The first row is back-filled with its own id as the recurrence group.
+        $this->db->shouldReceive('update')
+            ->once()
+            ->with('wp_us_availability', ['recurrence_group' => 10], ['id' => 10], ['%d'], ['%d']);
+
+        $first  = new AvailabilitySlot(5, '2026-04-07 09:00:00', '2026-04-07 10:00:00', 60);
+        $result = $this->repo->createWeeklySeries($first, 3);
+
+        self::assertSame([10, 11, 12], $result);
+        self::assertSame(
+            ['2026-04-07 09:00:00', '2026-04-14 09:00:00', '2026-04-21 09:00:00'],
+            $captured
+        );
+    }
+
     public function testFindByIdReturnsNullWhenNotFound(): void
     {
         $this->db->shouldReceive('prepare')
@@ -65,11 +96,14 @@ class AvailabilityRepositoryTest extends TestCase
     public function testFindByIdReturnsSlotWhenFound(): void
     {
         $row = (object) [
-            'id'            => '10',
-            'instructor_id' => '5',
-            'start_dt'      => '2026-04-01 09:00:00',
-            'end_dt'        => '2026-04-01 10:00:00',
-            'is_booked'     => '0',
+            'id'               => '10',
+            'instructor_id'    => '5',
+            'offering_id'      => null,
+            'start_dt'         => '2026-04-01 09:00:00',
+            'end_dt'           => '2026-04-01 10:00:00',
+            'duration_minutes' => '60',
+            'is_booked'        => '0',
+            'recurrence_group' => null,
         ];
 
         $this->db->shouldReceive('prepare')->andReturn('SELECT ...');
@@ -128,14 +162,32 @@ class AvailabilityRepositoryTest extends TestCase
         $this->repo->findAvailable(instructorId: 3);
     }
 
+    public function testFindAvailableWithOfferingAndDurationFilters(): void
+    {
+        $this->db->shouldReceive('prepare')
+            ->once()
+            ->with(
+                Mockery::pattern('/offering_id = %d AND duration_minutes = %d/'),
+                Mockery::on(static fn (array $p): bool => $p === [8, 30])
+            )
+            ->andReturn('SELECT ...');
+
+        $this->db->shouldReceive('get_results')->andReturn([]);
+
+        $this->repo->findAvailable(offeringId: 8, durationMinutes: 30);
+    }
+
     public function testFindByInstructorReturnsSlots(): void
     {
         $row = (object) [
-            'id'            => '5',
-            'instructor_id' => '3',
-            'start_dt'      => '2026-04-01 09:00:00',
-            'end_dt'        => '2026-04-01 10:00:00',
-            'is_booked'     => '0',
+            'id'               => '5',
+            'instructor_id'    => '3',
+            'offering_id'      => null,
+            'start_dt'         => '2026-04-01 09:00:00',
+            'end_dt'           => '2026-04-01 10:00:00',
+            'duration_minutes' => '60',
+            'is_booked'        => '0',
+            'recurrence_group' => null,
         ];
 
         $this->db->shouldReceive('prepare')->andReturn('SELECT ...');