feat(docs): version-bound release documentation served at /docs

Adds a docs pipeline so each release has a version-bound Markdown
document (docs/releases/vX.Y.Z.md) rendered publicly in the app:

- sync-release-docs.mjs copies docs/releases/*.md into the toolrate
  public dir and generates index.json before every dev/build
- /docs lists all releases; /docs/:version renders the sanitized
  Markdown (marked + DOMPurify, typography styles)
- template + workflow documented in docs/README.md
- current release (v0.6.0) documented as the first entry

artifacts/toolrate/src/App.tsx

@@ -20,6 +20,7 @@ import Trash from "@/pages/trash";
 import Compare from "@/pages/compare";
 import Watchlist from "@/pages/watchlist";
 import Login from "@/pages/login";
+import Docs from "@/pages/docs";
 import NotFound from "@/pages/not-found";
 
 const queryClient = new QueryClient({
@@ -46,6 +47,8 @@ function Router() {
       <Route path="/admin" component={Admin} />
       <Route path="/admin/redundancy" component={Redundancy} />
       <Route path="/trash" component={Trash} />
+      <Route path="/docs" component={Docs} />
+      <Route path="/docs/:version" component={Docs} />
       <Route component={NotFound} />
     </Switch>
   );