[FIX] Bind staging CLI to staging gateway

[HappySean2845]

Summary

• bake the environment-specific Surf gateway into release binaries
• make stg sync and lazy-sync fetch the staging OpenAPI spec
• scope the parsed API cache to its configured gateway
• document staging Equity verification commands

Test plan

• targeted Go tests for gateway selection and cache isolation
• go test ./... -run "^$" -count=1
• build with the staging ldflag and run surf sync
• list staging Equity operations
• call equity-company-profile --symbol AAPL --json against stg