Extract inline JS from public/index.html into ES modules #8

Context

public/index.html has grown to 1150+ lines with inline <script> containing the full Admin UI: state management, API client, DOM manipulation, history panel, file upload, autosave, etc. This makes it harder to navigate, test, and maintain.

Proposal

Extract the inline JS into ES modules under public/js/ (or similar), e.g.:

• api.js — fetch wrappers (api.list, api.snapshot, api.restore, etc.)
• state.js — shared UI state object
• ui.js — DOM manipulation, toast, badges, panel logic
• history.js — history panel fetch/select/restore flows

Load via <script type="module" src="..."> to keep the HTML as a thin shell.

References

• public/index.html — all inline JS
• PR feat: version history browser (CE3) #4 retrospective observation