feat(frontend): bootstrap Vite + React 19 + TS strict toolchain (F0.1)

- Vite 8 / React 19 / TS 6 strict (noUncheckedIndexedAccess, no baseUrl deprecation)
- Tailwind 4 via @tailwindcss/vite (no PostCSS step)
- TanStack Query 5, react-router-dom 7, Recharts, clsx
- Vitest + Testing Library + jsdom for unit tests
- Playwright skeleton + first smoke spec (login redirect)
- ESLint flat config: typescript-eslint type-checked, react-hooks, react-refresh, prettier
- Prettier config (semi, single quotes, 100-col, lf)
- IBM Plex font @font-face declarations targeting /fonts/ (self-host, no CDN — OPSEC)

frontend/public/fonts/README.md

@@ -0,0 +1,14 @@
+# IBM Plex — vendored fonts
+
+Drop the following .woff2 files here before merging to `main`:
+
+- `IBMPlexSans-{400,500,600,700}.woff2`
+- `IBMPlexSansCondensed-{500,600,700}.woff2`
+- `IBMPlexMono-{400,500,600}.woff2`
+
+Source: <https://github.com/IBM/plex> (OFL-1.1).
+
+Until they are vendored, the UI falls back to `ui-sans-serif` / `ui-monospace`
+via the `font-display: swap` directive — visually different but functional.
+
+Tracked as a sprint 0 chore (follow-up commit, not a blocker for the skeleton PR).