feat(frontend): provisional design system tokens + Logo placeholder (F0.2)

Aesthetic direction: instrumentation-grade telemetry (mission-control / SDR ops),
NOT shadcn defaults, NOT generic AI/SaaS. Mature palette: graphite surface scale,
CRT-amber for RT accent, steel-blue for SOC accent, sage/ochre/rust for detection
status — no neon, no rainbow.

Token layout designed to host the PR3 graphic charter without component churn:
  1. Primitives (--mc-*)        raw OKLCH scales
  2. Semantics (--accent-*, --status-*, --state-*, --surface-*, --line-*, …)
  3. Tailwind @theme mapping    semantic tokens → utilities

Includes:
- src/styles/theme.css       full token surface + base reset + scrollbars + grain
- src/styles/fonts.css       IBM Plex @font-face (self-host only)
- src/styles/globals.css     entry CSS file
- Logo (full/compact/mark) with corner-mark composition
- Panel, Pill, Button primitives reading exclusively from semantic tokens
- Logo.test.tsx (3 cases, Vitest + Testing Library)

frontend/src/styles/globals.css

@@ -0,0 +1,2 @@
+@import './fonts.css';
+@import './theme.css';