feat(datums): initial commit — unified datum creator addon

Standalone addon that replaces three stock PartDesign datum commands
(Plane, Line, Point) with a single unified Create_DatumCreator command.

Features:
- 16 smart creation modes (7 plane, 4 axis, 5 point)
- Auto-detection engine: selects best mode from geometry selection
- Mode override combo for manual selection
- Dynamic parameter UI (offset, angle, position, XYZ)
- Edit panel with real-time parameter updates via AttachExtension
- Catppuccin Mocha themed plane styling via SDK theme tokens
- Injected into partdesign.body and partdesign.feature contexts

Init.py

@@ -0,0 +1 @@
+"""Datums addon — console initialization (no-op)."""