feat: Provisionner automatiquement un nouvel établissement

Lorsqu'un super-admin crée un établissement via l'interface, le système
doit automatiquement créer la base tenant, exécuter les migrations,
créer le premier utilisateur admin et envoyer l'invitation — le tout
de manière asynchrone pour ne pas bloquer la réponse HTTP.

Ce mécanisme rend chaque établissement opérationnel dès sa création
sans intervention manuelle sur l'infrastructure.

backend/src/Scolarite/Application/Query/GetEvaluationDifficulty/EvaluationDifficultyDto.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Scolarite\Application\Query\GetEvaluationDifficulty;
+
+final readonly class EvaluationDifficultyDto
+{
+    public function __construct(
+        public string $evaluationId,
+        public string $title,
+        public string $classId,
+        public string $className,
+        public string $subjectId,
+        public string $subjectName,
+        public string $date,
+        public ?float $average,
+        public int $gradedCount,
+        public ?float $subjectAverage,
+        public ?float $percentile,
+    ) {
+    }
+}

backend/src/Scolarite/Application/Query/GetEvaluationDifficulty/GetEvaluationDifficultyHandler.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Scolarite\Application\Query\GetEvaluationDifficulty;
+
+use App\Scolarite\Application\Port\TeacherStatisticsReader;
+use App\Scolarite\Domain\Service\TeacherStatisticsCalculator;
+
+use function array_sum;
+use function count;
+use function round;
+
+use Symfony\Component\Messenger\Attribute\AsMessageHandler;
+
+#[AsMessageHandler(bus: 'query.bus')]
+final readonly class GetEvaluationDifficultyHandler
+{
+    public function __construct(
+        private TeacherStatisticsReader $reader,
+        private TeacherStatisticsCalculator $calculator,
+    ) {
+    }
+
+    /** @return list<EvaluationDifficultyDto> */
+    public function __invoke(GetEvaluationDifficultyQuery $query): array
+    {
+        $evaluations = $this->reader->teacherEvaluationDifficulties(
+            $query->teacherId,
+            $query->tenantId,
+        );
+
+        /** @var array<string, list<float>> $otherAveragesCache */
+        $otherAveragesCache = [];
+
+        $results = [];
+
+        foreach ($evaluations as $eval) {
+            /** @var string $subjectId */
+            $subjectId = $eval['subjectId'];
+
+            if (!isset($otherAveragesCache[$subjectId])) {
+                $otherAveragesCache[$subjectId] = $this->reader->subjectAveragesForOtherTeachers(
+                    $query->teacherId,
+                    $subjectId,
+                    $query->tenantId,
+                );
+            }
+
+            $otherAvgs = $otherAveragesCache[$subjectId];
+            $subjectAverage = $otherAvgs !== [] ? round(array_sum($otherAvgs) / count($otherAvgs), 2) : null;
+            $percentile = $eval['average'] !== null && $otherAvgs !== []
+                ? $this->calculator->calculatePercentile($eval['average'], $otherAvgs)
+                : null;
+
+            $results[] = new EvaluationDifficultyDto(
+                evaluationId: $eval['evaluationId'],
+                title: $eval['title'],
+                classId: $eval['classId'],
+                className: $eval['className'],
+                subjectId: $subjectId,
+                subjectName: $eval['subjectName'],
+                date: $eval['date'],
+                average: $eval['average'],
+                gradedCount: $eval['gradedCount'],
+                subjectAverage: $subjectAverage,
+                percentile: $percentile,
+            );
+        }
+
+        return $results;
+    }
+}

backend/src/Scolarite/Application/Query/GetEvaluationDifficulty/GetEvaluationDifficultyQuery.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Scolarite\Application\Query\GetEvaluationDifficulty;
+
+final readonly class GetEvaluationDifficultyQuery
+{
+    public function __construct(
+        public string $teacherId,
+        public string $tenantId,
+    ) {
+    }
+}