refactor: rewire silo submodule for silo-mod split

- .gitmodules: silo.git -> silo-mod.git (FreeCAD workbench only)
- Init.py: silo/pkg/freecad -> silo/freecad (new repo layout)
- InitGui.py: same path update

The silo monorepo has been split into:
- silo-client: shared Python API client (submodule of silo-mod)
- silo-mod: FreeCAD workbench (this submodule)
- silo-calc: LibreOffice Calc extension (separate repo)
- silo: server only (no longer a Create submodule)

.gitmodules

@@ -15,4 +15,4 @@
 	url = https://git.kindred-systems.com/forbes/ztools.git
 [submodule "mods/silo"]
 	path = mods/silo
-	url = https://git.kindred-systems.com/kindred/silo.git
+	url = https://git.kindred-systems.com/kindred/silo-mod.git

src/Mod/Create/Init.py

@@ -16,7 +16,7 @@ def setup_kindred_addons():
     # Define built-in addons with their paths relative to mods/
     addons = [
         ("ztools", "ztools/ztools"),  # mods/ztools/ztools/
-        ("silo", "silo/pkg/freecad"),  # mods/silo/pkg/freecad/
+        ("silo", "silo/freecad"),  # mods/silo/freecad/
     ]
 
     for name, subpath in addons:

src/Mod/Create/InitGui.py

@@ -15,7 +15,7 @@ def setup_kindred_workbenches():
 
     addons = [
         ("ztools", "ztools/ztools"),
-        ("silo", "silo/pkg/freecad"),
+        ("silo", "silo/freecad"),
     ]
 
     for name, subpath in addons: