Add configurable theme repo URL for SSH/HTTPS flexibility

- Default to SSH for local development
- Use HTTPS in GitLab CI via THEME_REPO_URL env var
- Maintain compatibility for both environments

Makefile

@@ -18,11 +18,13 @@ help:
 	@echo '   make devserver                      serve and regenerate together      '
 	@echo '                                                                          '
 
+THEME_REPO_URL ?= git@github.com:russellballestrini/pelican-svbhack.git
+
 venv:
 	python3 -m venv venv
 	venv/bin/pip install -r requirements.txt
 	mkdir -p pelican-themes
-	cd pelican-themes && git clone git@github.com:russellballestrini/pelican-svbhack.git
+	cd pelican-themes && git clone $(THEME_REPO_URL)
 	venv/bin/pelican-themes -i pelican-themes/pelican-svbhack/
 
 resume: