fix: don't error out if .venv exists when setting up

Makefile

@@ -1,8 +1,7 @@
 default: run
 
 setup:
-	@python3 -m venv .venv
-	@.venv/bin/pip install -r requirements.txt
+	@if [ ! -d ".venv" ]; then python3 -m venv .venv && .venv/bin/pip install -r requirements.txt; fi
 
 run:
 	@.venv/bin/python octomode.py