feat : export Excel et stats par tranche d'âge sur l'inventaire bovin

- Dépendance phpoffice/phpspreadsheet
- Endpoint GET /bovines/inventory-export : XLSX coloré, header figé, auto-filter, tri birthDate ASC
- Endpoint GET /bovines/inventory-stats : comptes par tranche d'âge (>=24, 22-24, 20-22)
- Bouton Excel à gauche du titre (style icône-only, même design que le bouton impression)
- Légende visuelle avec cartes bordées coloriées
- Ajustement seuils couleurs des lignes en -300 (base) / -400 (hover)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/State/Bovin/BovineInventoryStatsProvider.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\State\Bovin;
+
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProviderInterface;
+use App\ApiResource\BovineInventoryStats;
+use Doctrine\DBAL\Connection;
+
+/**
+ * @implements ProviderInterface<BovineInventoryStats>
+ */
+final class BovineInventoryStatsProvider implements ProviderInterface
+{
+    public function __construct(
+        private Connection $connection,
+    ) {}
+
+    public function provide(Operation $operation, array $uriVariables = [], array $context = []): BovineInventoryStats
+    {
+        $row = $this->connection->fetchAssociative(<<<'SQL'
+            SELECT
+                COUNT(*) AS total,
+                COUNT(*) FILTER (WHERE age_months >= 24) AS over_24,
+                COUNT(*) FILTER (WHERE age_months >= 22 AND age_months < 24) AS between_22_and_24,
+                COUNT(*) FILTER (WHERE age_months >= 20 AND age_months < 22) AS between_20_and_22
+            FROM bovine
+            WHERE exited_at IS NULL
+            SQL);
+
+        $stats                 = new BovineInventoryStats();
+        $stats->total          = (int) ($row['total'] ?? 0);
+        $stats->over24         = (int) ($row['over_24'] ?? 0);
+        $stats->between22And24 = (int) ($row['between_22_and_24'] ?? 0);
+        $stats->between20And22 = (int) ($row['between_20_and_22'] ?? 0);
+
+        return $stats;
+    }
+}