Fix #82: Add image path validation

[irusukan]

Overview

Fixes #82: Adds validation to skip empty image path inputs and reject spaces/dots-only inputs, preventing Hugo rendering errors.

Issue Details

Problems:

• Pressing Enter without input for the image path causes a site rendering error (render: failed to render pages).
• Similarly, inputs like " " or "." trigger the same error.

Reproduction Steps:

1. Launch blowfish-tools (v1.10.0).
2. Select "onfigure images".
3. Select any menu.
4. Enter "", " ", or "." and press Enter.
5. Run Hugo server to observe rendering error.

Cause:

Empty inputs cause normalizePath() to return ".", written to languages.en.toml as [params] logo = ".", triggering Hugo rendering errors.
Spaces or dots-only inputs (e.g., " ", ". ") also cause errors.

Changes

• Added empty input check to normalizePath() to skip configuration.
• Added enquirer validation (/^[\s.]+$/) to reject spaces/dots-only inputs with error message.

Testing

• Tested with "", " ", "." , " . . . ", confirming empty inputs are skipped and invalid inputs rejected.
• Verified valid inputs (e.g., /img/logo.png) work correctly.
• Ran Hugo server to ensure no errors.

Thanks for reviewing!