feat: phase A — backup B2, healthcheck /api/status, vector tiles Tippecanoe

- A1: scripts/backup-postgres.sh — pg_dump quotidien compressé → Backblaze B2 (rclone), rétention 30j
- A2: StatusController retourne HTTP 503 + healthy/alertReason si dernière observation > 6h
- A4: Dockerfile installe tippecanoe, GenerateTilesCommand génère 5 tilesets (obs + h6/12/24/48), Caddyfile sert /tiles/* sans fallback SPA, SargassesMap.jsx passe en sources vector tiles statiques
- chore: backend/public/assets/ ajouté au .gitignore (build artifacts)
- chore: setup vitest frontend + ImpactScoreServiceTest (session précédente)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/tests/Unit/Service/ImpactScoreServiceTest.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\Forecast\ImpactScoreService;
+use Doctrine\DBAL\Connection;
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\NullLogger;
+use Symfony\Component\Cache\Adapter\ArrayAdapter;
+use App\Service\Push\PushNotificationService;
+
+class ImpactScoreServiceTest extends TestCase
+{
+    private ImpactScoreService $service;
+
+    protected function setUp(): void
+    {
+        $connection = $this->createStub(Connection::class);
+        $em         = $this->createStub(EntityManagerInterface::class);
+        $cache      = new ArrayAdapter();
+        $push       = $this->createStub(PushNotificationService::class);
+
+        $this->service = new ImpactScoreService(
+            $connection,
+            $em,
+            $cache,
+            new NullLogger(),
+            $push,
+        );
+    }
+
+    // ── scoreToLevel ──────────────────────────────────────────────────────────
+
+    #[\PHPUnit\Framework\Attributes\DataProvider('scoreLevelProvider')]
+    public function testScoreToLevel(int $score, string $expected): void
+    {
+        $method = new \ReflectionMethod(ImpactScoreService::class, 'scoreToLevel');
+        $result = $method->invoke($this->service, $score);
+
+        self::assertSame($expected, $result);
+    }
+
+    /** @return array<string, array{int, string}> */
+    public static function scoreLevelProvider(): array
+    {
+        return [
+            'score 0 → low'        => [0,   'low'],
+            'score 30 → low'       => [30,  'low'],
+            'score 31 → medium'    => [31,  'medium'],
+            'score 70 → medium'    => [70,  'medium'],
+            'score 71 → high'      => [71,  'high'],
+            'score 100 → high'     => [100, 'high'],
+        ];
+    }
+
+    // ── emptyScore ────────────────────────────────────────────────────────────
+
+    public function testEmptyScoreReturnsCorrectStructure(): void
+    {
+        $method = new \ReflectionMethod(ImpactScoreService::class, 'emptyScore');
+        $result = $method->invoke($this->service);
+
+        self::assertSame(0,        $result['score']);
+        self::assertSame('low',    $result['level']);
+        self::assertNull($result['distance']);
+        self::assertSame(0.0,      $result['density']);
+        self::assertSame('stable', $result['trend']);
+        self::assertNull($result['etaHours']);
+    }
+}