Extension UI pass: a real design system instead of bare utility classes
- Replaced emoji type glyphs (πβοΈππΌοΈπΈπ) with a single consistent line-icon set (src/shared/components/Icon.tsx) β emoji render differently per OS and read as a placeholder rather than a finished interface.
- Popup: branded header with the shield mark, a hover-sweep on the primary button, icons on every action, and an animated save-confirmation panel instead of a plain paragraph.
- Vault dashboard: sidebar items get an active-state accent bar and per-section icons; item cards show a real image thumbnail for screenshots/saved images (via a shared useBlobUrl hook) instead of only a type glyph, plus a hover lift; the detail panel slides in instead of appearing instantly; empty states get an icon instead of just text.
- Added a small set of shared CSS utilities (brand-wash, shine, surface-interactive, nav-item) mirroring the website's design language at a fraction of the weight β no aurora, no scroll-driven animation, since a popup has to open instantly.