Rebuild the admin dashboard as a Svelte 5 + TypeScript app

Frontend in web/ (Vite via bun, pure CSS, no component libraries),
built to internal/dashboard/dist and embedded into the binary; the
Dockerfile builds it in a bun stage. Old static dashboard.html removed.

web/tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "strict": true,
+    "verbatimModuleSyntax": true,
+    "isolatedModules": true,
+    "skipLibCheck": true,
+    "noEmit": true,
+    "types": ["svelte", "vite/client"]
+  },
+  "include": ["src/**/*.ts", "src/**/*.svelte", "vite.config.ts"]
+}