IFC tutorial scripts broken with compas_ifc 1.7.0 and compas_viewer 2.x

## Environment
- OS: Windows 11
- Python: 3.12
- compas_ifc: 1.7.0
- compas_viewer: 2.0.2
- ifcopenshell: 0.8.5

## Problem
The tutorial scripts `viewer.py`, `spatial_tree.py`, and `attribute_tree.py`
use outdated APIs that no longer work with current package versions.

## Fixes required

### viewer.py / spatial_tree.py / attribute_tree.py

**1. `body_with_opening` no longer exists**
```python
# OLD
viewer.add(entity.body_with_opening, name=entity.name)
# NEW
geom = entity.geometry
if geom:
viewer.scene.add(geom, name=entity.name)
```

**2. `viewer.add()` no longer exists → use `viewer.scene.add()`**

**3. `from compas_viewer.layout import Treeform` no longer exists**
```python
# OLD
from compas_viewer.layout import Treeform
# NEW
from compas_viewer.components.treeform import Treeform
```

**4. `from compas_ifc.entities import Entity` no longer exists**
```python
# OLD
from compas_ifc.entities import Entity
# NEW
from compas_ifc.entities.base import Base as Entity
```

**5. `viewer.layout.sidedock.add_element()` no longer exists**
```python
# OLD
viewer.layout.sidedock.add_element(Treeform(...))
# NEW
treeform = Treeform(...)
treeform.update() # required to populate the widget
viewer.ui.sidedock.add(treeform)
```

**6. Treeform columns API changed**
```python
# OLD
Treeform(tree, {"Name": ".name", "Value": ".attributes['value']"})
# NEW
Treeform(tree, columns={"Name": lambda n: n.name,
"Value": lambda n: n.attributes.get("value", "")})
```

**7. Scale needed for correct geometry size (IFC units are in mm)**
```python
from compas.geometry import Scale
S = Scale.from_factors([0.001, 0.001, 0.001])
geom.transform(S)
```