Splitting privileged tests into *_privileged_test.go left their shared helpers in
the untagged files, so in the default (no-tag) build they had no callers and
golangci-lint flagged them as unused.
Moved the privileged-only helpers into the privileged files next to their callers
(generateDummyHandler; createEngine/startSignal/startManagement/getConnectedPeers/
getPeers + kaep/kasp; (*mockDaemon).setJWTToken). Annotated the shared routing-test
fixtures that must stay untagged for cross-platform compilation with //nolint:unused
(systemops_bsd expected* vars, ensureIPv6DefaultRoute on bsd/windows,
loopbackIfaceWindows), matching the existing linux variant.