* refactor(config): extract registerFlags from Parse
split flag registration into a registerFlags helper so callers, including
tests, can build and inspect the flag set without parsing os.Args. pure
move, no behavior change.
* feat(config): add scan templates via -template
wire up the existing -template flag to load a batch of scan settings from
a built-in preset or a local yaml file, so a run does not have to pass
every flag by hand.
a value is a named preset (minimal, recon, full) embedded in the binary,
or a path to a local yaml file keyed by flag long-names. it merges as the
goflags config before parsing, so command-line flags still win and it
replaces the ambient config for that run.
implements #5.
