CAM: Remove colons from labels, fix lint, and update imports

Removed explicit colons from all form labels.
Fixed lint warnings and replaced wildcard imports with explicit
imports for clarity and maintainability.

src/Mod/CAM/Path/Machine/ui/editor/machine_editor.py:
- Removed ':' from all form labels
- Fixed lint warnings (missing docstrings, empty except, etc.)
- Replaced wildcard imports with explicit imports

src/Mod/CAM/Path/Machine/models/__init__.py:
- Updated __all__ and imports for explicit API

src/Mod/CAM/Path/Tool/assets/ui/preferences.py:
- Updated imports to use package-level import

src/Mod/CAM/Path/Machine/models/machine.py:
- Added explanatory comments to empty except blocks
- Fixed duplicate variable assignment
- Added missing class docstrings

src/Mod/CAM/CAMTests/TestMachine.py:
- Fixed unused variable warning by using returned filepath

src/Mod/CAM/CAMTests/TestMachine.py

@@ -11,10 +11,8 @@
 # ***************************************************************************
 
 import FreeCAD
-import unittest
 import tempfile
 import pathlib
-import json
 import CAMTests.PathTestUtils as PathTestUtils
 from Path.Machine.models.machine import (
     Machine,
@@ -406,7 +404,7 @@ class TestMachineFactory(PathTestUtils.PathTestBase):
 
         # Save and load
         filepath = MachineFactory.save_configuration(machine, "complex.fcm")
-        loaded = MachineFactory.load_configuration("complex.fcm")
+        loaded = MachineFactory.load_configuration(filepath)
 
         # Verify all components
         self.assertEqual(loaded.name, machine.name)