Add automatic aur_builder and yay setup for Arch-based systems

- Added aur_builder_setup target to Makefile
- Automatically detects Arch/Manjaro via pacman
- Creates aur_builder user and group with sudoers permissions
- Installs yay if not already present
- Skips AUR setup gracefully on non-Arch systems

https://chatgpt.com/share/68f2a922-63f8-800f-a6d6-18b8d06b7139

Makefile

@@ -1,4 +1,4 @@
-.PHONY: install setup uninstall
+.PHONY: install setup uninstall aur_builder_setup
 
 setup: install
 	@python3 main.py install
@@ -23,8 +23,33 @@ install:
 		rc_line='if [ -d "$${HOME}/.venvs/pkgmgr" ]; then . "$${HOME}/.venvs/pkgmgr/bin/activate"; echo "Global Python virtual environment '\''~/.venvs/pkgmgr'\'' activated."; fi'; \
 		grep -qxF "$${rc_line}" $$rc || echo "$${rc_line}" >> $$rc; \
 	done
+	@echo "Arch/Manjaro detection and optional AUR setup..."
+	@if command -v pacman >/dev/null 2>&1; then \
+		$(MAKE) aur_builder_setup; \
+	else \
+		echo "Not Arch-based (no pacman). Skipping aur_builder/yay setup."; \
+	fi
 	@echo "Installation complete. Please restart your shell (or 'exec bash' or 'exec zsh') for the changes to take effect."
 
+# Only runs on Arch/Manjaro
+aur_builder_setup:
+	@echo "Setting up aur_builder and yay (Arch/Manjaro)..."
+	@sudo pacman -Syu --noconfirm
+	@sudo pacman -S --needed --noconfirm base-devel git sudo
+	@# group & user
+	@if ! getent group aur_builder >/dev/null; then sudo groupadd -r aur_builder; fi
+	@if ! id -u aur_builder >/dev/null 2>&1; then sudo useradd -m -r -g aur_builder -s /bin/bash aur_builder; fi
+	@# sudoers rule for pacman
+	@echo '%aur_builder ALL=(ALL) NOPASSWD: /usr/bin/pacman' | sudo tee /etc/sudoers.d/aur_builder >/dev/null
+	@sudo chmod 0440 /etc/sudoers.d/aur_builder
+	@# yay install (if missing)
+	@if ! sudo -u aur_builder bash -lc 'command -v yay >/dev/null'; then \
+		sudo -u aur_builder bash -lc 'cd ~ && rm -rf yay && git clone https://aur.archlinux.org/yay.git && cd yay && makepkg -si --noconfirm'; \
+	else \
+		echo "yay already installed."; \
+	fi
+	@echo "aur_builder/yay setup complete."
+
 uninstall:
 	@echo "Removing global user virtual environment if it exists..."
 	@rm -rf ~/.venvs/pkgmgr