v0.15.5: Disaster recovery — Hub-based infra backup, auto-mount, restore UI

Complete DR implementation (TASK2.md Phases 1-4):
- Hub infra-backup push/pull endpoints (controller.yaml, disk layout, stacks)
- Fresh-deployment detection pulls config from Hub, auto-mounts drives by UUID
- Full-page restore UI with drive status, app table, sequential restore
- docker-setup.sh shows DR instructions when customer_id is configured

New files: disk_layout.go, restore_scan.go, restore_app_linux.go,
restore_drives_linux.go, infra_backup.go, infra_pull.go,
handler_restore.go, restore.html

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

controller/internal/backup/restore_app_other.go

@@ -0,0 +1,13 @@
+//go:build !linux
+
+package backup
+
+import (
+	"context"
+	"log"
+)
+
+// RestoreAppFromBackup is a no-op on non-Linux platforms.
+func RestoreAppFromBackup(ctx context.Context, app *RestorableApp, stacksDir string, logger *log.Logger) error {
+	return nil
+}