* fix(backend): respect start flags in all commands
Currently flags like --externalDomain do only work in the last
registered command which currently is start-from-setup.
This creates the flags globally in the init function in uses them for
all start commands.
* fix(backend): remove viper defaults in start flags
At this point viper is not yet initialized so this defaults would have
not effect either.
* Remove flag name variables and run go mod tidy
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Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>
