[Feature]: support for light-theme terminal

### 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_