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/disk_layout.go

@@ -0,0 +1,19 @@
+package backup
+
+// DiskLayout holds the fstab-derived mount topology for disaster recovery.
+type DiskLayout struct {
+	Mounts []DiskMount `json:"mounts"`
+}
+
+// DiskMount represents a single mount entry from fstab.
+type DiskMount struct {
+	UUID         string `json:"uuid"`
+	Label        string `json:"label"`
+	MountPoint   string `json:"mount_point"`
+	FSType       string `json:"fs_type"`
+	SizeBytes    int64  `json:"size_bytes"`
+	FstabOptions string `json:"fstab_options"`
+	Role         string `json:"role"`        // "system_data", "hdd_storage"
+	BindSubdir   string `json:"bind_subdir"` // e.g., "felhom_data"
+	RawMount     string `json:"raw_mount"`   // e.g., "/mnt/.felhom-raw/hdd_1"
+}