feat(ui): implement InstaChef design system

- Replace Tailwind with IC CSS design tokens (purple/pink/orange brand gradient,
  Lilita One / DM Sans / JetBrains Mono fonts, light+dark theme via data-theme)
- Add all SVG icon components (ic/Bell, BellOff, Check, Chevron, Clipboard,
  Close, Download, External, Filter, Link, Plus, Retry, Search, Settings,
  Share, Spark, Trash, PhasePrepping, PhaseSimmering, PhasePlating)
- Add shared primitives: Chip, RecipeThumb (deterministic gradient swatch),
  CookingPot (animated SVG), PhaseTrack, SectionHead
- Add TopBar with LIVE indicator and notification bell
- Add CookingHero: animated hero card for in-progress items
- Add TimelineRow: queue list row with status badges
- Add EmptyState: gradient hero + dismissible How it works card
- Add RecipeSheet: bottom-sheet detail overlay with phase progress
- Add AddUrlScreen: full-page URL input with clipboard paste
- Add NotificationsScreen: push toggle + SSE status
- Rewrite +page.svelte: screen router (home/addurl/notifs) + RecipeSheet;
  preserves all SSE, retry, remove, filter, auto-subscribe logic
- Rewrite share/+page.svelte: uses AddUrlScreen shell, preserves Share Target
  logic and auto-process on URL param
- Rewrite InstallPrompt.svelte: InstallSheet bottom-sheet design, all PWA logic intact
- Update manifest.json theme_color to #FFF8F5
- 282 unit tests passing (unchanged)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

static/manifest.json

@@ -4,8 +4,8 @@
   "start_url": "/",
   "scope": "/",
   "display": "standalone",
-  "theme_color": "#ffffff",
-  "background_color": "#ffffff",
+  "theme_color": "#FFF8F5",
+  "background_color": "#FFF8F5",
   "icons": [
     {
       "src": "/favicon.png",