Freezmo: self-hosted notes-to-activities study app

Next.js 15 app that turns photos, PDFs, DOCX/PPTX and text into a swipeable
feed of AI-generated activities (flashcards, multiple choice, true/false,
fill-in-the-blank, matching, ordering, short answer) using the user's own
Ollama models.

Highlights:
- All AI calls run in server route handlers; the browser never talks to Ollama.
- Bring-your-own-key mode (default): the key lives only in the browser and is
  sent per-request; server, local-daemon and shared-key modes also supported.
- Client-side document extraction (pdf.js, mammoth, jszip) with scanned-PDF
  page rendering for the vision model; notes stay in their original language.
- ChatGPT-style shell: collapsible sidebar / mobile drawer, neutral token-based
  light + dark themes, folder organisation, PWA (manifest, SW, offline page).
- Strict JSON validation with zod + auto-repair, rate limiting, and request
  guards (cross-origin, body-size, API-key sanitising).
- setup.sh bootstraps deps, .env.local and a production build.

Gitignore excludes .env*, the generated pdf.js worker and local scratch files.

lib/nav.ts

@@ -0,0 +1,72 @@
+"use client";
+
+/**
+ * Folder selection lives outside React so the sidebar (desktop) and the folder
+ * pills (mobile) can drive the same view.
+ */
+
+import { useSyncExternalStore } from "react";
+
+export const ALL_FOLDERS = "all";
+
+let selected = ALL_FOLDERS;
+const listeners = new Set<() => void>();
+
+export const folderSelection = {
+  subscribe(listener: () => void): () => void {
+    listeners.add(listener);
+    return () => listeners.delete(listener);
+  },
+  getSnapshot(): string {
+    return selected;
+  },
+  getServerSnapshot(): string {
+    return ALL_FOLDERS;
+  },
+  set(id: string): void {
+    if (selected === id) return;
+    selected = id;
+    listeners.forEach((listener) => listener());
+  },
+};
+
+/* Mobile drawer ---------------------------------------------------------- */
+
+let drawerOpen = false;
+const drawerListeners = new Set<() => void>();
+
+export const sidebarOpen = {
+  subscribe(listener: () => void): () => void {
+    drawerListeners.add(listener);
+    return () => drawerListeners.delete(listener);
+  },
+  getSnapshot(): boolean {
+    return drawerOpen;
+  },
+  getServerSnapshot(): boolean {
+    return false;
+  },
+  set(value: boolean): void {
+    drawerOpen = value;
+    drawerListeners.forEach((listener) => listener());
+  },
+  toggle(): void {
+    sidebarOpen.set(!drawerOpen);
+  },
+};
+
+export function useSidebarOpen(): boolean {
+  return useSyncExternalStore(
+    sidebarOpen.subscribe,
+    sidebarOpen.getSnapshot,
+    sidebarOpen.getServerSnapshot,
+  );
+}
+
+export function useSelectedFolder(): string {
+  return useSyncExternalStore(
+    folderSelection.subscribe,
+    folderSelection.getSnapshot,
+    folderSelection.getServerSnapshot,
+  );
+}