feat(pwa): installable PWA + responsive mobile dashboard

- Add Web App Manifest + ArbPulse icons (192/512/maskable/apple-touch) under
  web/public/; no service worker (real-time honesty: never serve stale data).
- Add mobile/install metadata to index.html (theme-color, viewport-fit=cover,
  apple-mobile-web-app-*, manifest + apple-touch-icon links).
- Responsive layout: PriceMatrix stacked per-venue cards below sm, StatsBar
  reflow, ~44px touch targets in Controls/ConfigPanel, safe-area top inset.
- scripts/gen-icons.ps1 derives icon sizes from the master (no new deps).
- openspec: add-pwa-mobile change (proposal/design/specs/tasks).

Co-authored-by: Cursor <cursoragent@cursor.com>

openspec/changes/add-pwa-mobile/tasks.md

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+## 1. Icons
+
+- [x] 1.1 Finalize the ArbPulse master icon and derive `icon-192.png`,
+      `icon-512.png`, `icon-maskable-512.png` (glyph within ~80% safe zone), and
+      `apple-touch-icon.png` (180px)
+- [x] 1.2 Place all icons under `web/public/`
+
+## 2. Manifest
+
+- [x] 2.1 Create `web/public/manifest.webmanifest` with `name`, `short_name`,
+      `start_url: "/"`, `scope: "/"`, `display: "standalone"`,
+      `theme_color`/`background_color` `#0a0e14`, and icon entries (192, 512, and
+      512 maskable with `"purpose": "maskable"`)
+
+## 3. HTML head metadata
+
+- [x] 3.1 In `web/index.html`, add `viewport-fit=cover` to the viewport meta and a
+      `theme-color` meta (`#0a0e14`)
+- [x] 3.2 Add `<link rel="manifest">`, `<link rel="apple-touch-icon">`, and the
+      `apple-mobile-web-app-capable` / `apple-mobile-web-app-status-bar-style` /
+      `apple-mobile-web-app-title` tags
+
+## 4. Responsive layout
+
+- [x] 4.1 `PriceMatrix.tsx`: render per-venue stacked cards (exchange + bid/ask/qty/
+      spread as label–value rows) below `sm`; keep the `<table>` from `sm` up, with
+      no horizontal overflow on phones
+- [x] 4.2 `StatsBar.tsx`: reflow stats and badges on mobile without clipping
+- [x] 4.3 Ensure touch targets in `Controls.tsx` and `ConfigPanel.tsx` are ~44px min
+- [x] 4.4 Sanity-check `App.tsx` spacing/padding on narrow viewports
+
+## 5. Verify
+
+- [x] 5.1 `npm run typecheck` and `npm test` pass
+- [x] 5.2 `npm run build` succeeds and `web/dist` contains the manifest + icons
+- [x] 5.3 DevTools device emulation: no horizontal overflow at ~375px; Application →
+      Manifest shows no errors; confirm no service worker is registered
+- [ ] 5.4 After `dev → PR → main → deploy.sh`, install on a real phone from
+      `https://arbpulse.wayool.com` and confirm standalone launch + live SSE data