[Feature]: support for light-theme terminal

[matejcik]

Problem Statement

The specify CLI is using terminal colors in a way that doesn't fit light-background-dark-text configs

picture is worth a thousand words:

Proposed Solution

A configuration option should allow changing terminal theme to light.

Alternatives Considered

No response

Component

Specify CLI (initialization, commands)

AI Agent (if applicable)

None

Use Cases

1. when working in a light-themed terminal

Acceptance Criteria

• ability to switch to a light theme is offered either during initial setup or as a command-line flag + config file toggle
• when enabled, all text is easily readable in a terminal emulator set to light theme

Additional Context

No response