feat(10-01): serve the embedded admin SPA at backend.uri with cookie login

- backend.uri prefix (default /backend) mounts the admin API at {prefix}/api/v1
  and the embedded SPA shell at {prefix} with an api/ JSON 404 fallback
- cookie transport: an X-Requested-With login sets the HttpOnly summer_admin
  cookie and returns no token; the backend guard reads the cookie after Bearer
- CSRF wrapper refuses cookie-only POST/PUT/DELETE without X-Requested-With
- boardwalk package embeds boardwalk/dist, rewrites index.html once per prefix
  and sets cache and security headers
- framework admin OpenAPI pipeline (swag, swagger2openapi, openapi-typescript)
  with prefix-relative paths and typed envelopes for the tracer routes
- admin/ Vite SPA: login, plugin rail, section panel and read-only list
  through the openapi-fetch client typed by the generated schema

admin/tsconfig.json

@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedIndexedAccess": true,
+    "verbatimModuleSyntax": true,
+    "isolatedModules": true,
+    "resolveJsonModule": true,
+    "skipLibCheck": true,
+    "noEmit": true,
+    "jsx": "preserve",
+    "types": []
+  },
+  "include": ["src/**/*.ts", "src/**/*.vue", "tests/**/*.ts", "env.d.ts"]
+}