교사로서의 디지털 윤리 강화하기

Add a shared legal footer to every page of this web app.

Use the two attached Markdown files as the only source of truth:
1. 이용약관.md
2. 개인정보처리방침.md

Do not invent, rewrite, summarize, or remove clauses from the attached documents.

Footer content:
- Left: copyright notice using the actual service name
- Center: privacy officer or service contact information from the attached documents
- Right: two links labeled "이용약관" and "개인정보처리방침"

Implementation requirements:
1. Create one reusable shared footer component.
2. Render it through the global app layout so it appears consistently on every page.
3. Do not manually duplicate the footer inside individual pages.
4. Match the existing design system, colors, typography, spacing, and responsive layout.
5. Keep all visible UI text in Korean.
6. Use a horizontal three-part layout on desktop.
7. Stack the footer content vertically on mobile.
8. Add a subtle top border and sufficient spacing.
9. Preserve all existing pages, navigation, data, and functionality.

When the user selects "이용약관":
- open an accessible modal
- render the complete Markdown content of 이용약관.md
- display the effective date clearly
- provide Print, Markdown Download, and Close buttons

When the user selects "개인정보처리방침":
- open an accessible modal
- render the complete Markdown content of 개인정보처리방침.md
- display the effective date clearly
- provide Print, Markdown Download, and Close buttons

Modal requirements:
- close button in the top-right corner
- close with the Escape key
- close when the backdrop is selected
- lock background scrolling while open
- trap keyboard focus inside the modal
- return focus to the original footer link after closing
- support long documents with internal scrolling
- use a near-full-screen layout on mobile
- provide readable heading, paragraph, list, and spacing styles

Download requirements:
- download the original attached Markdown content
- preserve Korean characters using UTF-8
- use a real .md filename
- do not download rendered HTML

Important:
- Do not add data collection methods that the app does not use.
- Do not claim that data is stored only in localStorage if the app also uses a cloud database.
- Do not claim that no personal information is processed if nickname, class code, login, analytics, or user records are stored.
- Do not expose API keys, secrets, internal UUIDs, or private database values.
- Do not change unrelated components or pages.

After implementation, test:
- footer visibility on every page
- both policy links
- keyboard and Escape-key behavior
- mobile layout
- print behavior
- Markdown file downloads
- Korean text encoding
- consistency between the displayed documents and downloaded files