feat: implement profile management commands

[joshrotenberg]

Summary

Implements the missing profile management commands: set, remove, and default.

Features

Profile Set

• Create new profiles or update existing ones
• Overwrite protection with confirmation prompt
• Password prompting for Enterprise profiles when not provided via CLI
• Automatic suggestion to set as default for first/only profile

Profile Remove

• Delete profiles with confirmation prompt
• Warning when removing the default profile
• Clears default profile if the removed profile was default

Profile Default

• Set the default profile
• Validates that the profile exists

Safety Features

• ✅ Confirmation prompts before overwriting existing profiles
• ✅ Confirmation prompts before removing profiles
• ✅ Warning when removing the default profile
• ✅ Secure password entry for Enterprise profiles
• ✅ Profile existence validation

Testing

# List profiles
redisctl profile list

# Set default profile
redisctl profile default cloud

# Create new profile (with overwrite protection)
redisctl profile set test-cloud --deployment cloud --api-key KEY --api-secret SECRET

# Remove profile (with confirmation)
redisctl profile remove test-cloud

Fixes #181

Release Note

This is a feature addition that will trigger a minor version bump (v0.3.0 → v0.4.0) when merged.