Add the appliance web UI look, interface names, MCP and REST API, local zone

Web UI: dark/light themes (appliance layout, sidebar, switch checkboxes),
theme preference on the Advanced page, Changes page with the pending diff.

Interface names: router.interfaces.<name>.mac, lans.<l>.deviceName and
pppoe.vlanName; a rename is staged for the next reboot by router-apply.

Remote access: an MCP server (POST /mcp) and an OpenAPI REST API
(/api/v1, /api/openapi.json) with the same tokens, scopes, limits and audit
log; tools to read status, settings, leases, logs (get_logs), and to edit
and check the saved settings (never applied). Tokens on the API access page.

Firewall: a reserved `local` zone (the router itself) as the destination of
rules, so the web UI or SSH can be allowed from the WAN.

PLAN.md lists what is still left.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F

pkgs/router-webui/collect.go

@@ -70,6 +70,7 @@ type SystemStatus struct {
 	Load        string
 	Kernel      string  // the running kernel
 	KernelNext  string  // the kernel of the current system when it differs: a reboot is due
+	BootPending bool    // a configuration is staged for the next boot (interface names)
 	CPU         float64 // percent; NaN until the second sample
 	MemUsed     uint64
 	MemTotal    uint64
@@ -262,6 +263,14 @@ func systemStatus() SystemStatus {
 	if dest, err := filepath.EvalSymlinks("/run/current-system/kernel"); err == nil {
 		s.KernelNext = pendingKernel(s.Kernel, dest)
 	}
+	// router-apply sets the system profile without activating it when the
+	// configuration changes interface names. (While a change awaits
+	// confirmation the two differ too, but a rollback timer is running.)
+	if cur, err := filepath.EvalSymlinks("/run/current-system"); err == nil {
+		if prof, err := filepath.EvalSymlinks("/nix/var/nix/profiles/system"); err == nil && prof != cur {
+			s.BootPending = rollbackIn() == 0
+		}
+	}
 	if data, err := os.ReadFile("/proc/loadavg"); err == nil {
 		if f := strings.Fields(string(data)); len(f) >= 3 {
 			s.Load = strings.Join(f[:3], " ")