feat: add AWS profile-based authentication for Bedrock

[mehmetozturk4705]

Summary

• Add AWS profile authentication for Bedrock — supports SSO, IAM keys, assumed roles, and any profile type as an alternative to bearer token auth. The CLI mounts ~/.aws/ read-only into the worker container for credential resolution
• Extend setup wizard with auth method selection — Bedrock setup now prompts for token vs. profile auth, validates profile credentials at setup time, and surfaces actionable errors for expired SSO sessions
• Update credential validation across CLI and worker — preflight checks, config resolver, and env forwarding all handle the new AWS_PROFILE path with mutual exclusivity against bearer token mode

Closes #268