Add basic auth deprecation warnings for May 3rd retirement

[samsolaimani]

Summary

• Displays a yellow bordered warning banner every time a command runs using basic auth (password), directing users to migrate to OAuth2
• Adds the same deprecation warning at the start of alks developer login
• Updates the password choice label in alks developer configure to reflect the May 3rd retirement date
• Adds a "did you mean?" tip when a user has configured https://alks.coxautoinc.com without the required /rest path

Test plan

Basic auth deprecation warning

• Run any alks command (e.g. sessions open) configured with basic auth — confirm the yellow deprecation warning banner appears in the terminal
• Run alks developer login — confirm warning appears before credential prompts
• Run alks developer configure — confirm password choice shows "(DEPRECATED - retiring May 3rd, not recommended)"
• Run any command configured with OAuth2 (refresh token) — confirm no warning appears

"Did you mean?" server URL hint

• Set ALKS_SERVER=https://alks.coxautoinc.com and run alks sessions open — confirm the yellow tip appears: "Did you mean https://alks.coxautoinc.com/rest?"
• Set ALKS_SERVER=https://alks.coxautoinc.com/ (trailing slash) and run alks sessions open — confirm tip still appears
• Set ALKS_SERVER=https://alks.coxautoinc.com/rest and run alks sessions open — confirm no tip appears
• Set a completely different server URL — confirm no tip appears

Rally

US1879500: Create warning for ALKS CLI basic auth deprecation