fix: untrack runtime config files and add them to .gitignore

These files are machine-specific and generated at runtime — they should
never have been committed. Remove from index (files kept on disk) and
add explicit gitignore rules to prevent future re-adds.

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

.gitignore

@@ -16,6 +16,22 @@ config/wireguard/
 *.crt
 *.pem
 
+# Runtime-generated config files (machine-specific, generated at startup)
+config/api/caddy/Caddyfile
+config/api/calendar.json
+config/api/cell_config.json
+config/api/wireguard.json
+config/api/webdav/webdav.conf
+config/api/dhcp/
+config/caddy/Caddyfile
+config/dhcp/dnsmasq.conf
+config/dns/Corefile
+config/mail/mailserver.env
+config/mail/config/dovecot-quotas.cf
+config/ntp/chrony.conf
+config/radicale/
+config/webdav/users.passwd
+
 # Logs
 *.log
 logs/