Add full shell, replaceable Omics adapter and bilingual interaction

Implement approved specification #32 and tickets #33-#37. Keep host authentication server-verified and pin session interaction language. Compile scoped base selectors for browser compatibility and retain full gutters during CSS pruning.

frontend/src/hooks/useUnsavedDraft.ts

@@ -0,0 +1,18 @@
+import { useEffect, useState } from "react";
+
+/** Protect edits until reverted or unmounted after the host accepts the response. */
+export function useUnsavedDraft(draft: string, active = true) {
+  const [initialDraft] = useState(draft);
+  const dirty = active && draft !== initialDraft;
+
+  useEffect(() => {
+    if (!dirty) return;
+    const protectDraft = (event: BeforeUnloadEvent) => {
+      event.preventDefault();
+      // The browser supplies its own localized warning.
+      event.returnValue = "";
+    };
+    window.addEventListener("beforeunload", protectDraft);
+    return () => window.removeEventListener("beforeunload", protectDraft);
+  }, [dirty]);
+}