fix: make update stashes runtime config before pull to avoid merge conflicts

Runtime config files exist on disk but are now gitignored. A bare git pull
conflicts with them. Stash (including untracked) before pulling and pop after.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -127,7 +127,9 @@ shell-%:
 
 update:
 	@echo "Pulling latest code..."
+	@git stash --include-untracked --quiet 2>/dev/null || true
 	git pull
+	@git stash pop --quiet 2>/dev/null || true
 	@if [ ! -f config/mail/mailserver.env ]; then \
 	  echo "Config missing — running setup first..."; \
 	  $(MAKE) setup; \