Settings : upload image fond page d'accueil

- Section "Image d'accueil" dans settings.php (par famille)
- Stockage dans /uploads/home_bg_{family_id}.{ext}
- Aperçu de l'image actuelle + bouton reset vers le défaut
- /home-bg.php : endpoint sécurisé pour servir l'image
- index.php : override inline CSS si image personnalisée

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

home-bg.php

@@ -0,0 +1,18 @@
+<?php
+require __DIR__ . '/includes/auth.php';
+require_login();
+
+$family_id = $_SESSION['user']['family_id'];
+if (!$family_id) { http_response_code(404); exit; }
+
+$file = null;
+foreach (glob('/uploads/home_bg_' . $family_id . '.*') as $f) { $file = $f; break; }
+
+if (!$file || !file_exists($file)) { http_response_code(404); exit; }
+
+$ext  = strtolower(pathinfo($file, PATHINFO_EXTENSION));
+$mime = ['jpg'=>'image/jpeg','jpeg'=>'image/jpeg','png'=>'image/png','webp'=>'image/webp'][$ext] ?? 'image/jpeg';
+
+header('Content-Type: ' . $mime);
+header('Cache-Control: private, max-age=3600');
+readfile($file);