feat: Permettre l'import d'élèves via fichier CSV ou XLSX

L'import manuel élève par élève est fastidieux pour les établissements
qui gèrent des centaines d'élèves. Un wizard d'import en 4 étapes
(upload → mapping → preview → confirmation) permet de traiter un
fichier complet en une seule opération, avec détection automatique
du format (Pronote, École Directe) et validation avant import.

L'import est traité de manière asynchrone via Messenger pour ne pas
bloquer l'interface, avec suivi de progression en temps réel et
réutilisation des mappings entre imports successifs.

backend/tests/Unit/Administration/Application/Service/Import/ColumnMappingSuggesterTest.php

@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Administration\Application\Service\Import;
+
+use App\Administration\Application\Service\Import\ColumnMappingSuggester;
+use App\Administration\Domain\Model\Import\KnownImportFormat;
+use App\Administration\Domain\Model\Import\StudentImportField;
+
+use function count;
+
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+use const SORT_REGULAR;
+
+final class ColumnMappingSuggesterTest extends TestCase
+{
+    private ColumnMappingSuggester $suggester;
+
+    protected function setUp(): void
+    {
+        $this->suggester = new ColumnMappingSuggester();
+    }
+
+    #[Test]
+    public function suggestPronoteMapping(): void
+    {
+        $columns = ['Élèves', 'Né(e) le', 'Sexe', 'Adresse E-mail', 'Classe de rattachement'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::PRONOTE);
+
+        self::assertSame(StudentImportField::FULL_NAME, $mapping['Élèves']);
+        self::assertSame(StudentImportField::BIRTH_DATE, $mapping['Né(e) le']);
+        self::assertSame(StudentImportField::GENDER, $mapping['Sexe']);
+        self::assertSame(StudentImportField::EMAIL, $mapping['Adresse E-mail']);
+        self::assertSame(StudentImportField::CLASS_NAME, $mapping['Classe de rattachement']);
+    }
+
+    #[Test]
+    public function suggestEcoleDirecteMapping(): void
+    {
+        $columns = ['NOM', 'PRENOM', 'CLASSE', 'DATE_NAISSANCE', 'SEXE'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::ECOLE_DIRECTE);
+
+        self::assertSame(StudentImportField::LAST_NAME, $mapping['NOM']);
+        self::assertSame(StudentImportField::FIRST_NAME, $mapping['PRENOM']);
+        self::assertSame(StudentImportField::CLASS_NAME, $mapping['CLASSE']);
+        self::assertSame(StudentImportField::BIRTH_DATE, $mapping['DATE_NAISSANCE']);
+        self::assertSame(StudentImportField::GENDER, $mapping['SEXE']);
+    }
+
+    #[Test]
+    public function suggestGenericMappingByKeywords(): void
+    {
+        $columns = ['Nom', 'Prénom', 'Classe', 'Email'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::CUSTOM);
+
+        self::assertSame(StudentImportField::LAST_NAME, $mapping['Nom']);
+        self::assertSame(StudentImportField::FIRST_NAME, $mapping['Prénom']);
+        self::assertSame(StudentImportField::CLASS_NAME, $mapping['Classe']);
+        self::assertSame(StudentImportField::EMAIL, $mapping['Email']);
+    }
+
+    #[Test]
+    public function suggestDoesNotDuplicateFields(): void
+    {
+        $columns = ['Nom', 'Nom de famille', 'Prénom', 'Classe'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::CUSTOM);
+
+        $mappedFields = array_values($mapping);
+        $uniqueFields = array_unique($mappedFields, SORT_REGULAR);
+
+        self::assertCount(count($uniqueFields), $mappedFields);
+    }
+
+    #[Test]
+    public function suggestHandlesUnknownColumns(): void
+    {
+        $columns = ['ColonneInconnue', 'AutreColonne', 'Nom', 'Classe'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::CUSTOM);
+
+        self::assertArrayNotHasKey('ColonneInconnue', $mapping);
+        self::assertArrayNotHasKey('AutreColonne', $mapping);
+        self::assertArrayHasKey('Nom', $mapping);
+        self::assertArrayHasKey('Classe', $mapping);
+    }
+
+    #[Test]
+    public function suggestHandlesEnglishColumnNames(): void
+    {
+        $columns = ['Last Name', 'First Name', 'Class', 'Email'];
+
+        $mapping = $this->suggester->suggerer($columns, KnownImportFormat::CUSTOM);
+
+        self::assertSame(StudentImportField::LAST_NAME, $mapping['Last Name']);
+        self::assertSame(StudentImportField::FIRST_NAME, $mapping['First Name']);
+        self::assertSame(StudentImportField::CLASS_NAME, $mapping['Class']);
+        self::assertSame(StudentImportField::EMAIL, $mapping['Email']);
+    }
+}