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>

src/Availability/AvailabilityRepository.php

@@ -15,24 +15,78 @@ class AvailabilityRepository {
 		$this->db->insert(
 			$this->table,
 			[
-				'instructor_id' => $slot->instructorId,
-				'start_dt'      => $slot->startDt,
-				'end_dt'        => $slot->endDt,
-				'is_booked'     => 0,
-				'created_at'    => current_time( 'mysql' ),
+				'instructor_id'    => $slot->instructorId,
+				'offering_id'      => $slot->offeringId,
+				'start_dt'         => $slot->startDt,
+				'end_dt'           => $slot->endDt,
+				'duration_minutes' => $slot->durationMinutes,
+				'is_booked'        => 0,
+				'recurrence_group' => $slot->recurrenceGroup,
+				'created_at'       => current_time( 'mysql' ),
 			],
-			[ '%d', '%s', '%s', '%d', '%s' ]
+			[ '%d', '%d', '%s', '%s', '%d', '%d', '%d', '%s' ]
 		);
 
 		return $this->db->insert_id;
 	}
 
 	/**
-	 * Find unbooked slots, optionally filtered by instructor and date range.
+	 * Create a weekly-recurring series from a template slot. Each occurrence is a
+	 * separate row one week apart, all sharing a `recurrence_group` (the id of the
+	 * first row).
+	 *
+	 * @return list<int> Inserted slot IDs.
+	 */
+	public function createWeeklySeries( AvailabilitySlot $first, int $occurrences ): array {
+		$occurrences = max( 1, $occurrences );
+		$start       = new \DateTimeImmutable( $first->startDt );
+		$end         = new \DateTimeImmutable( $first->endDt );
+
+		$ids     = [];
+		$groupId = 0;
+
+		for ( $week = 0; $week < $occurrences; $week++ ) {
+			$shift = '+' . ( 7 * $week ) . ' days';
+
+			$id = $this->insert(
+				new AvailabilitySlot(
+					instructorId:    $first->instructorId,
+					startDt:         $start->modify( $shift )->format( 'Y-m-d H:i:s' ),
+					endDt:           $end->modify( $shift )->format( 'Y-m-d H:i:s' ),
+					durationMinutes: $first->durationMinutes,
+					offeringId:      $first->offeringId,
+					recurrenceGroup: $groupId > 0 ? $groupId : null,
+				)
+			);
+
+			if ( 0 === $groupId ) {
+				$groupId = $id;
+				$this->setRecurrenceGroup( $id, $groupId );
+			}
+
+			$ids[] = $id;
+		}
+
+		return $ids;
+	}
+
+	private function setRecurrenceGroup( int $id, int $groupId ): void {
+		$this->db->update(
+			$this->table,
+			[ 'recurrence_group' => $groupId ],
+			[ 'id' => $id ],
+			[ '%d' ],
+			[ '%d' ]
+		);
+	}
+
+	/**
+	 * Find unbooked slots, optionally filtered by instructor, offering, lesson
+	 * length, and date range.
 	 *
 	 * @return list<AvailabilitySlot>
 	 */
-	public function findAvailable( int $instructorId = 0, string $from = '', string $to = '' ): array {
+	public function findAvailable( int $instructorId = 0, int $offeringId = 0, int $durationMinutes = 0, string $from = '', string $to = '' ): array {
 		$where  = [ 'is_booked = 0' ];
 		$params = [];
 
@@ -41,6 +95,16 @@ class AvailabilityRepository {
 			$params[] = $instructorId;
 		}
 
+		if ( $offeringId > 0 ) {
+			$where[]  = 'offering_id = %d';
+			$params[] = $offeringId;
+		}
+
+		if ( $durationMinutes > 0 ) {
+			$where[]  = 'duration_minutes = %d';
+			$params[] = $durationMinutes;
+		}
+
 		if ( '' !== $from ) {
 			$where[]  = 'start_dt >= %s';
 			$params[] = $from;