feat: add ACME account management with validation pipeline

- Register, view, and deactivate ACME accounts via API and UI
- 16-check validation framework for certificate issuance readiness
- DNS resolution, port, nginx, and firewall pre-flight checks
- External IP detection with NAT support and fallback providers
- Account card and settings modal in certificates page
- Guard certificate issuance behind account registration
- Update modal CSS to overlay-based approach
- 1000+ lines of tests for validation and account handlers

system/systemd/vacuum-walld.service

@@ -19,7 +19,7 @@ Environment=HOME={{ PROJECT_DIR }}
 
 # Security hardening
 ProtectSystem=strict
-ReadWritePaths={{ PROJECT_DIR }} /tmp /etc/systemd/network /etc/nginx /etc/dnsmasq.d /etc/wireguard /run/sudo /run/firewalld
+ReadWritePaths={{ PROJECT_DIR }} /tmp /etc/systemd/network /etc/nginx /etc/dnsmasq.d /etc/wireguard /run/sudo /run/firewalld /run/nginx
 PrivateTmp=yes
 ProtectKernelTunables=yes
 ProtectKernelModules=yes