Fix AuthProfile deserialization for social login profiles

[syedair]

Summary

• Adds #[serde(alias = "profileName")] to AuthProfile.profile_name so it deserializes correctly from both snake_case and camelCase JSON
• Adds unit tests for both deserialization formats

Problem

The wrapper binary (q_cli/fig_auth) writes the auth profile to the database with camelCase:

{"arn":"...","profileName":"Social_Default_Profile"}

But AuthProfile in chat-cli expects snake_case (profile_name), causing get_auth_profile() to fail with:

Failed to get auth profile: missing field `profile_name` at line 1 column 114

This results in profileArn being None, which triggers the lazy ListAvailableProfiles fallback. When that also fails (returns empty for social auth tokens), users see:

profileArn is required but no profiles are available. Please log in and select a profile.

Debug log (KIRO_LOG_LEVEL=debug KIRO_CHAT_LOG_FILE=/tmp/debug.log) confirms this:

ERROR chat_cli::api_client: 350: Failed to get auth profile: missing field `profile_name` at line 1 column 114
INFO  chat_cli::api_client: 194: profileArn missing, attempting lazy resolution via list_available_profiles

Verification

Running the chat binary directly after manually fixing the JSON to "profile_name" confirms chat works. The #[serde(alias)] fix makes this automatic.

Test plan

• Unit tests pass for both profile_name and profileName JSON formats
• Social/Google login users can send chat messages without the profileArn error
• Builder ID and IAM Identity Center login flows remain unaffected

Fixes #3703