feat: add a booking event history for admins

Admins get /admin/history: one line per booking created, rescheduled or
released, per series created or ended, and per resource deleted with its
bookings. Sortable by time, kind, resource, booked day and both people;
filterable by period, kinds, who acted and resource type.

Events are snapshots written inside the same transaction as the change,
so a rolled-back booking leaves none and a released booking stays
readable. app:booking-events:prune keeps twelve months and needs a cron
entry on the server.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

migrations/Version20261016135717.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * The event history behind /admin/history. Starts empty: the audit log file covers the time
+ * before it, and is not imported.
+ */
+final class Version20261016135717 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Adds the booking event history';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('CREATE TABLE booking_event (id INT AUTO_INCREMENT NOT NULL, occurred_at DATETIME NOT NULL, type VARCHAR(32) NOT NULL, actor_name VARCHAR(100) NOT NULL, holder_name VARCHAR(100) DEFAULT NULL, resource_id INT DEFAULT NULL, resource_label VARCHAR(50) NOT NULL, resource_type VARCHAR(32) NOT NULL, date DATE DEFAULT NULL, end_date DATE DEFAULT NULL, start_minute INT DEFAULT NULL, end_minute INT DEFAULT NULL, previous_start_minute INT DEFAULT NULL, previous_end_minute INT DEFAULT NULL, booking_id INT DEFAULT NULL, series_id INT DEFAULT NULL, details JSON NOT NULL, actor_id INT DEFAULT NULL, holder_id INT DEFAULT NULL, INDEX idx_booking_event_occurred_at (occurred_at), INDEX idx_booking_event_actor_occurred_at (actor_id, occurred_at), INDEX IDX_AAD2F71210DAF24A (actor_id), INDEX IDX_AAD2F712DEEE62D0 (holder_id), PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4');
+        $this->addSql('ALTER TABLE booking_event ADD CONSTRAINT FK_AAD2F71210DAF24A FOREIGN KEY (actor_id) REFERENCES `user` (id) ON DELETE SET NULL');
+        $this->addSql('ALTER TABLE booking_event ADD CONSTRAINT FK_AAD2F712DEEE62D0 FOREIGN KEY (holder_id) REFERENCES `user` (id) ON DELETE SET NULL');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE booking_event DROP FOREIGN KEY FK_AAD2F71210DAF24A');
+        $this->addSql('ALTER TABLE booking_event DROP FOREIGN KEY FK_AAD2F712DEEE62D0');
+        $this->addSql('DROP TABLE booking_event');
+    }
+}