module smartcamera: does not load

Venv installed by environment-install-ubuntu script.

```
STABILIZE> module load smartcamera
STABILIZE> Failed to load module: No module named 'smartcamera'. Use 'set moddebug 3' in the MAVProxy console to enable traceback

STABILIZE>
STABILIZE> set moddebug 3
STABILIZE> module load smartcamera
STABILIZE> No module named 'sc_webcam'
Traceback (most recent call last):
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 690, in import_package
mod = __import__(name)
File "/home/andre/venv-ardupilot/lib/python3.13/site-packages/MAVProxy/modules/mavproxy_smartcamera/__init__.py", line 39, in
from sc_webcam import SmartCameraWebCam
ModuleNotFoundError: No module named 'sc_webcam'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 373, in load_module
m = import_package(modpath)
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 693, in import_package
mod = __import__(name)
File "/home/andre/venv-ardupilot/lib/python3.13/site-packages/MAVProxy/modules/mavproxy_smartcamera/__init__.py", line 39, in
from sc_webcam import SmartCameraWebCam
ModuleNotFoundError: No module named 'sc_webcam'

No module named 'smartcamera'
Traceback (most recent call last):
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 690, in import_package
mod = __import__(name)
ModuleNotFoundError: No module named 'smartcamera'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 373, in load_module
m = import_package(modpath)
File "/home/andre/venv-ardupilot/bin/mavproxy.py", line 693, in import_package
mod = __import__(name)
ModuleNotFoundError: No module named 'smartcamera'

Failed to load module: No module named 'smartcamera'.

```

Reproduce the failure after using the environment-install-ubuntu script by running `module load smartcamera` with `set moddebug 3` in MAVProxy. Read `MAVProxy/modules/mavproxy_smartcamera/__init__.py` and trace the `sc_webcam` import shown in the traceback. Done means the smartcamera module loads successfully without the reported import errors.

Written by the indexing model from the issue text.