Refactor disk-usage logic into dedicated script

Move disk-usage functionality from Makefile to a dedicated shell script
for better maintainability and consistency with other scripts.

Changes:
- Create scripts/disk-usage.sh with all disk usage logic
- Simplify Makefile disk-usage target to call the script
- Add environment loading and color formatting to script
- Fix duplicate output by adding head -1 to grep chain

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

scripts/disk-usage.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+#
+# Script d'affichage de l'espace disque du serveur de backup
+# Usage: ./disk-usage.sh
+#
+
+set -e
+
+# Couleurs
+BLUE='\033[0;34m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+# Charger et exporter les variables d'environnement
+if [ -f /etc/borgmatic/.env ]; then
+    set -a
+    source /etc/borgmatic/.env
+    set +a
+elif [ -f .env ]; then
+    set -a
+    source .env
+    set +a
+fi
+
+echo -e "${BLUE}Espace disque sur le serveur de backup:${NC}"
+echo ""
+
+# Statistiques du repository Borg
+echo -e "${YELLOW}Espace utilisé par le repository Borg (toutes archives):${NC}"
+borgmatic info 2>/dev/null | grep "All archives" | grep GB | head -1
+
+echo ""
+
+# Espace libre sur le serveur distant
+echo -e "${YELLOW}Espace libre sur le serveur distant:${NC}"
+USER_HOST=$(echo $BORG_REPO | sed "s|ssh://||" | sed "s|:.*||")
+PORT=$(echo $BORG_REPO | grep -o ":[0-9]*/" | sed "s|[:/]||g")
+
+if [ -n "$PORT" ]; then
+    ssh -p $PORT $USER_HOST "df -h ~/ | tail -1"
+else
+    ssh $USER_HOST "df -h ~/ | tail -1"
+fi