[verified] Security hardening + UX/UI polish
Security (requesting-code-review pipeline + independent reviewer):
- Fix path traversal on file upload (basename sanitize + resolve-containment)
- Fix IDOR: org + owner scoping on all group/chat routes (_authorize_group/_get_owned_group),
hide other users' personal groups in listings
- Remove XSS via v-html in Chat task (text interpolation)
- Add test_security.py (traversal + cross-user denial) — all pass
UX/UI (ui-ux-pro-max + frontend-dev-verification):
- Global: focus rings, 44px touch targets, hover/press transitions, input focus glow,
prefers-reduced-motion, skeleton loaders, empty states, back links, spinner
- Login: password toggle, autocomplete, spinner, disabled-when-empty
- Cards lift on hover; dashboard skeleton + empty state; analyze button spinner
All backend tests pass (m0/m1/routes/security/e2e); frontend builds; served SPA verified via curl.
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