feat: add gateway setup wizard and fix test suite

New zt-gateway-setup script with subcommands for configuring this
router as a ZeroTier exit gateway: bridge, routing (tables 100/101),
DHCP, hotplug, and persistence. Exposes setup ubus method via backend
with ACL and LuCI panel in overview.

Also fixes two pre-existing test issues:
- overview.spec.ts: active gateway radio is intentionally enabled
  (users need to re-trigger switch for the already-selected gateway)
- drain.spec.ts: stubs drain status via page.route() since Docker
  has no real conntrack entries; fixed Playwright glob pattern bug
  where **/ubus* fails to match /ubus/?timestamp (regex needed)

root/usr/share/rpcd/ucode/zt-gateway.uc

@@ -181,10 +181,6 @@ return {
 					return { success: false, message: `Unknown gateway region: ${region}` };
 				}
 
-				const current_region = read_active_region();
-				if (current_region === region && !drain_active()) {
-					return { success: true, message: `Already on ${region}.` };
-				}
 
 				const result = run_switch_script_capture(gw.ip, mode);
 				if (result.code !== 0) {
@@ -297,6 +293,39 @@ return {
 						: (result.stderr || `Cancel failed with code ${result.code}`)
 				};
 			}
+		},
+
+		setup: {
+			args: {
+				command: 'string'
+			},
+			call: function(req) {
+				const command = req.args?.command;
+				if (!command || !match(command, /^(status|setup-bridge|setup-routing|setup-dhcp|setup-hotplug|setup-persistence|setup-all)$/)) {
+					return {
+						success: false,
+						message: 'Invalid command. Valid: status, setup-bridge, setup-routing, setup-dhcp, setup-hotplug, setup-persistence, setup-all'
+					};
+				}
+
+				const stderr_pipe = '/tmp/zt-gw-setup-stderr';
+				const code = system(`/usr/sbin/zt-gateway-setup ${shell_quote(command)} 2>${stderr_pipe}`);
+				const err = fs.readfile(stderr_pipe) ?? '';
+				fs.unlink(stderr_pipe);
+
+				if (code !== 0) {
+					return {
+						success: false,
+						message: trim(err) || `Setup failed with exit code ${code}`
+					};
+				}
+
+				return {
+					success: true,
+					message: trim(err) || `${command} completed successfully`,
+					command: command
+				};
+			}
 		}
 	}
 };