Port the init wizard and config test from jira-ticket-cli PR #59.

Files to create:

• tools/jtk/internal/cmd/initcmd/initcmd.go - jtk init command

Features:

jtk init - Interactive setup wizard:

• Prompts for URL, email, API token
• Verifies connection before saving (--no-verify to skip)
• Non-interactive mode: --url, --email, --token flags
• Detects existing config, prompts for overwrite

jtk config test - Connectivity verification:

• Tests authentication and API access
• Clear pass/fail with troubleshooting suggestions

Source: open-cli-collective/jira-ticket-cli#59