chore: scaffold Mudfish VPN decky plugin

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main.py

@@ -0,0 +1,14 @@
+import os
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "py_modules"))
+
+import decky  # noqa: E402
+
+
+class Plugin:
+    async def _main(self):
+        decky.logger.info("Mudfish VPN plugin loaded")
+
+    async def _unload(self):
+        decky.logger.info("Mudfish VPN plugin unloaded")