feat: add hardware specs to nodes (CPU, RAM, Disk) with canvas display

- Add cpu_count, cpu_model, ram_gb, disk_gb, show_hardware fields to NodeData
- NodeModal: collapsible Hardware section with toggle to show specs on canvas
- BaseNode: 2-line hardware section with Cpu/MemoryStick/HardDrive icons, only renders set fields
- DetailPanel: Hardware section with GB/TB formatting
- Backend: schema, model, DB migration, canvas save/load support
- Tests: frontend (NodeModal, DetailPanel) + backend (canvas persist/load)

backend/app/schemas/canvas.py

@@ -23,6 +23,11 @@ class NodeSave(BaseModel):
     container_mode: bool = False
     custom_colors: dict[str, Any] | None = None
     custom_icon: str | None = None
+    cpu_count: int | None = None
+    cpu_model: str | None = None
+    ram_gb: float | None = None
+    disk_gb: float | None = None
+    show_hardware: bool = False
     pos_x: float = 0
     pos_y: float = 0