feat: warn user when modules can be loaded twice.

Solara by default assumes the name for `solara run <name>` is a
directory. However, when the name is also a package, which imports
module from the package, the package modules can be loaded twice.
Solara will execute the python files in the directory, while Python
will load the python files as modules from the package.
This can leads to unexpected behavior, such as reactive variables
existing twice.

solara/server/app.py

@@ -98,6 +98,14 @@ def add_path():
             # resolve the directory, because Path("file").parent.parent == "." != ".."
             self.directory = self.path.resolve()
             routes = solara.generate_routes_directory(self.path)
+
+            if any(name for name in sys.modules.keys() if name.startswith(self.name)):
+                logger.warn(
+                    f"Directory {self.name} is also used as a package. This can cause modules to be loaded twice, and might "
+                    "cause unexpected behavior. If you run solara from a different directory (e.g. the parent directory) you "
+                    "can avoid this ambiguity."
+                )
+
         elif self.name.endswith(".py"):
             self.type = AppType.SCRIPT
             add_path()