feat(design): animated design system foundation with animate-ui and motion

Install motion + animate-ui, overhaul design tokens with brand cyan accent,
and replace CSS keyframe animations in Dialog, Tabs, Switch, and Tooltip
with spring-physics and blur-fade transitions via animate-ui Radix primitives.

frontend/src/lib/get-strict-context.tsx

@@ -0,0 +1,36 @@
+import * as React from 'react';
+
+function getStrictContext<T>(
+  name?: string,
+): readonly [
+  ({
+    value,
+    children,
+  }: {
+    value: T;
+    children?: React.ReactNode;
+  }) => React.JSX.Element,
+  () => T,
+] {
+  const Context = React.createContext<T | undefined>(undefined);
+
+  const Provider = ({
+    value,
+    children,
+  }: {
+    value: T;
+    children?: React.ReactNode;
+  }) => <Context.Provider value={value}>{children}</Context.Provider>;
+
+  const useSafeContext = () => {
+    const ctx = React.useContext(Context);
+    if (ctx === undefined) {
+      throw new Error(`useContext must be used within ${name ?? 'a Provider'}`);
+    }
+    return ctx;
+  };
+
+  return [Provider, useSafeContext] as const;
+}
+
+export { getStrictContext };