fix: pass __file__ to exec() in addon Init.py/InitGui.py loading

DirMod.run_init() and DirModGui.run_init_gui() use exec(code) to run
addon Init.py and InitGui.py files, but don't pass __file__ in the
globals dict. Addons that reference __file__ (e.g. Silo) crash with
NameError: name '__file__' is not defined.

Pass {"__file__": str(init_py)} as the globals argument so __file__
is available in the executed code, matching the behavior of normal
Python module loading.

src/App/FreeCADInit.py

@@ -1204,7 +1204,7 @@ class DirMod(Mod):
         try:
             source = init_py.read_text(encoding="utf-8")
             code = compile(source, init_py, 'exec')
-            exec(code)
+            exec(code, {"__file__": str(init_py)})
         except Exception as ex:
             Log(f"Init:      Initializing {self.path!s}... failed")
             Log(utils.HLine)

src/Gui/FreeCADGuiInit.py

@@ -295,7 +295,7 @@ class DirModGui(ModGui):
             try:
                 source = init_gui_py.read_text(encoding="utf-8")
                 code = compile(source, init_gui_py, "exec")
-                exec(code)
+                exec(code, {"__file__": str(init_gui_py)})
             except Exception as ex:
                 sep = "-" * 100 + "\n"
                 Log(f"Init:      Initializing {target!s}... failed\n")