[dark-mode] Phase 4.4: Update project documentation (README, DEVELOPMENT.md)

- README.md: Add dark mode to Features list
- DEVELOPMENT.md: Add Prerequisites section with Node.js >= 18 requirement
- DEVELOPMENT.md: Document nedb -> @seald-io/nedb migration (Node 24 compat)
- DEVELOPMENT.md: Add Dark Mode section and Testing section
- progress-report.md: Mark Phase 4.4 as done

Author: Hunta

.github/specs/dark-mode/documentation/progress-report.md

@@ -35,7 +35,7 @@
 | **4.1** | Code review & cleanup | ✅ Done |
 | **4.2** | Unit tests for ThemeManager | ✅ Done |
 | **4.3** | Developer documentation (audit & prune outdated docs) | ✅ Done |
-| **4.4** | Update project documentation (README, DEVELOPMENT.md) | Not Started |
+| **4.4** | Update project documentation (README, DEVELOPMENT.md) | ✅ Done |
 | **5.1** | Prepare for merge (rebase, PR) | Not Started |
 | **5.2** | Deploy & monitor | Not Started |
 

DEVELOPMENT.md

@@ -27,9 +27,15 @@ touch docs-config.local.yaml
 yarn dev
 ```
 
+## Prerequisites
+
+- **Node.js ≥ 18** (tested up to Node 24)
+
+> **Note on NeDB:** The local database driver was migrated from the original [`nedb`](https://www.npmjs.com/package/nedb) package (unmaintained since 2016) to [`@seald-io/nedb`](https://github.com/seald/nedb). The original `nedb` crashes on Node.js ≥ 24 because it relies on removed `util.isDate()` / `util.isRegExp()` functions. The `@seald-io/nedb` fork is a drop-in replacement that supports modern Node.js versions. No data migration is needed — the on-disk format is identical.
+
 ## Starting docs with MongoDB
 
-By default, the application uses a local database powered by [nedb](https://www.npmjs.com/package/nedb).
+By default, the application uses a local database powered by [@seald-io/nedb](https://github.com/seald/nedb) (a maintained fork of nedb).
 In order to use MongoDB, follow these steps:
 
 
@@ -65,6 +71,38 @@ Run it with
 node bin/db-converter --db-path=./db --mongodb-uri=mongodb://localhost:27017/docs
 ```
 
+## Dark Mode
+
+The application includes a dark mode that can be toggled via the sun/moon button in the header. Theme preference is saved to `localStorage` and persists across sessions. If no preference is saved, the system `prefers-color-scheme` setting is used.
+
+The theme system uses CSS custom properties defined in `src/frontend/styles/vars.pcss` (light defaults) and `src/frontend/styles/dark-mode.pcss` (dark overrides via `[data-theme="dark"]`). The `ThemeManager` module (`src/frontend/js/modules/themeManager.js`) handles initialization, persistence, and theme switching.
+
+All dark mode colors follow WCAG 2.1 AA contrast requirements.
+
+## Testing
+
+### Unit Tests
+
+```shell
+yarn test
+```
+
+### E2E Tests (Playwright)
+
+Runs across Chromium, Firefox, and WebKit:
+
+```shell
+yarn test:e2e
+```
+
+Interactive UI mode:
+
+```shell
+yarn test:e2e:ui
+```
+
+The E2E suite auto-starts the dev server on port 7777. Test files are in `src/test/e2e/`.
+
 ## Using S3 uploads driver
 
 Uploads driver is used to store files uploaded by users.

README.md

@@ -14,6 +14,7 @@ It's super easy to install and use.
 - 📂 Docs nesting — create any structure you need
 - 💎 Static rendering
 - 📱 Nice look on Desktop and Mobile
+- 🌙 Dark mode — system preference detection, manual toggle, localStorage persistence
 - 🔥 Beautiful page URLs. Human-readable and SEO-friendly.
 - 🦅 [Hawk](https://hawk.so/?from=docs-demo) is hunting. Errors tracking integrated
 - 💌 [Misprints](https://github.com/codex-team/codex.misprints) reports to the Telegram / Slack