feat(redesign): design-system tokens, 23 Vue components, game-aware shell + Fleet/Solo dashboard

Tokens ported 1:1 from the Claude Design bundle (colors/game-themes/type/spacing/elevation/motion/fonts) with the data-theme/data-game theming contract via useThemeGame (+ cc-skin-swap repaint guard). 23 design-system components reimplemented as Vue SFCs (core/forms/data/navigation/feedback/brand). DashboardLayout rebuilt as the game-aware shell (GameSwitcher, grouped nav with permission gating preserved, agent-health footer, topbar). DashboardView: Fleet + Solo with per-game GAME_FIELDS rows and the themed ECharts PlayersChart; Solo wired to the real server store, Fleet on representative data pending the multi-instance backend. All four game skins (Rust/Dune/Conan/Soulmask). vue-tsc + vite build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/assets/corrosion-mark.svg

@@ -0,0 +1,8 @@
+<svg viewBox="0 0 64 64" fill="none" xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Corrosion">
+  <path d="M40.2 9.45 A24 24 0 0 1 54.6 23.8" stroke="currentColor" stroke-width="6.4" stroke-linecap="round"></path>
+  <path d="M54.6 40.2 A24 24 0 0 1 40.2 54.6" stroke="currentColor" stroke-width="6.4" stroke-linecap="round"></path>
+  <path d="M23.8 54.6 A24 24 0 0 1 9.45 40.2" stroke="currentColor" stroke-width="6.4" stroke-linecap="round"></path>
+  <path d="M9.45 23.8 A24 24 0 0 1 23.8 9.45" stroke="currentColor" stroke-width="6.4" stroke-linecap="round"></path>
+  <path d="M32 16V24M32 40V48M16 32H24M40 32H48" stroke="currentColor" stroke-width="3.6" stroke-linecap="round"></path>
+  <circle cx="32" cy="32" r="4.4" fill="currentColor"></circle>
+</svg>