feat: DashboardService with per-source cache and stale fallback, FixtureSource

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/WeatherSource.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Weerscherm;
+
+/** Ruwe data van de drie upstream-bronnen. Implementaties: LiveSource (echte API's) en FixtureSource (voorbeelddata). */
+interface WeatherSource
+{
+    /** @return array<string, mixed> de "body" van Netatmo getstationsdata */
+    public function stationsData(): array;
+
+    /** @return array<string|int, mixed> de "body" van Netatmo getmeasure (timestamp => [mm]) */
+    public function measure(string $deviceId, string $moduleId, int $begin, int $end): array;
+
+    /** @return array<string, mixed> het "daily"-blok van Open-Meteo */
+    public function forecast(float $lat, float $lon, string $timezone): array;
+}