[client] categorize root/system-mutating tests behind a privileged build tag

Tests that need root or mutate host state (nftables/iptables/DNS, TUN/WireGuard
interfaces, routes, eBPF, SSH/service install) are now gated behind a
//go:build privileged tag. The default `go test ./client/...` runs as a non-root
user with no sudo and leaves host networking untouched; mixed files were split so
pure-logic tests stay in the default suite.

A self-hosting ory/dockertest/v4 harness (client/testutil/privileged) runs the
privileged suite inside a --privileged --cap-add=NET_ADMIN container via
`make test-privileged`; a DOCKER_CI=true guard skips the spawn when already inside
the container. Added `make test-unit` for the host-safe run.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: lint lint-all lint-install setup-hooks
+.PHONY: lint lint-all lint-install setup-hooks test-unit test-privileged
 GOLANGCI_LINT := $(shell pwd)/bin/golangci-lint
 
 # Install golangci-lint locally if needed
@@ -25,3 +25,13 @@ setup-hooks:
 	@git config core.hooksPath .githooks
 	@chmod +x .githooks/pre-push
 	@echo "✅ Git hooks configured! Pre-push will now run 'make lint'"
+
+# Host-safe unit tests: excludes the privileged-tagged tests (root / system-mutating).
+# Runs as a normal user with no sudo and leaves host networking untouched.
+test-unit:
+	@go test -tags devcert -timeout 10m ./...
+
+# Privileged suite: runs the `privileged`-tagged tests inside a --privileged
+# --cap-add=NET_ADMIN container via the ory/dockertest harness. Requires Docker.
+test-privileged:
+	@go test -tags 'devcert privileged' -timeout 30m -run TestRunPrivilegedSuiteInDocker -v ./client/testutil/privileged/...