* [Rewards] Make gate3 URL environment-aware via CLI switches
* Address review: network audit list, public_deps, CHECK
- Add gate3 prod and dev endpoints to network audit allowed list
- Move //base to public_deps in :constants (BS-024)
- Replace DCHECK with CHECK in GetGate3URL (CS-025)
* Fix broken tests
* Remove gate3 endpoints from network audit list
* Add gate3 endpoints to TLS pin list
* Replace auto with explicit type
* Refactor GetGate3URL tests into table-driven loop
* Move kEnvGate3Switch to header and use named constants in tests
* Add explicit default for gate3_url in RewardsEngineOptions
* Fix MaybeWarnSwitchValue comment to describe both log paths
* Remove gate3 entries from brave_network_audit_allowed_lists.h
* Simplify GetGate3URL to delegate to GetServicesDomain
* Use std::optional<std::string> for gate3_url instead of empty sentinel
* Rename brave_domains/constants.h/cc to urls.h/cc
* Switch to GURL in GetGate3URL
* Clean up review nits from gate3 env switch
* Add comment in brave_domains/urls.h
Anirudha Bose
a667af3258