docs: add screenshots and Korean README

[flowylife]

Purpose

Improve the public GitHub landing page by showing real App X-Ray screenshots and linking a Korean README page.

Changes

• Add desktop screenshots for the review workbench, app map, and export readiness views.
• Add a mobile review screenshot captured from the rendered app.
• Add a Korean README page at README.ko.md.
• Link the Korean page from the English README.

Verification

• Rendered app with Vite dev server and captured screenshots with Playwright.
• Mobile screenshot check: viewport width 390, scrollWidth 390, reviewRows 39.
• Console issues during capture: none.
• git diff --check.
• README and README.ko.md link targets verified locally.

User Flow Checked

• Page checked: local App X-Ray dev server.
• Action performed: created a sample project, ran Mock analysis, opened review/app-map/export views, and captured screenshots.
• Observed result: screenshots render realistic seeded UI states and mobile layout remains within viewport width.

Risk Areas

• DB schema changed: No
• API contract changed: No
• Auth/permission changed: No
• UI layout changed: No
• State management changed: No
• Data import/export changed: No
• Build/deployment config changed: No
• Test coverage changed: No

Merge Note

Safe to merge after CI passes. This is documentation and image asset work only.