Add user database migration, core reusable components, and layout structure

web/lib/store.mjs

@@ -0,0 +1,10 @@
+export function createStore(initial) {
+  let state = { ...initial };
+  const subscribers = new Set();
+
+  return {
+    get()           { return { ...state }; },
+    set(updates)    { state = { ...state, ...updates }; subscribers.forEach(fn => fn(state)); },
+    subscribe(fn)   { subscribers.add(fn); return () => subscribers.delete(fn); },
+  };
+}