feat: add VitePress docs site, music file picker modal, Dockerfile optimization, i18n keys for 14 locales

- Add docs/ with VitePress site (19 pages): guide, config, architecture, FAQ
- Add GitHub Actions workflow for auto-deploy to GitHub Pages
- Replace music 'Add Tracks' upload picker with in-app audio file browser modal
- Add music picker CSS styles with dark theme support
- Add missing i18n keys (search_audio, no_audio_files, etc.) to all 14 locales
- Optimize Dockerfile: shared base stage, COPY --chmod, consolidated RUN, HEALTHCHECK
- Improve README: docs links, updated stats (222+ tests, 14 languages), feature status

docs/faq.md

@@ -0,0 +1,79 @@
+# FAQ
+
+## General
+
+### What is OxiCloud?
+
+OxiCloud is a self-hosted cloud platform written in Rust. It provides file storage, calendar sync, contacts sync, and office editing from a single binary.
+
+### How does it compare to NextCloud?
+
+OxiCloud uses ~20× less RAM, produces a ~25× smaller Docker image, and starts in under 1 second. The trade-off is fewer plugins — OxiCloud builds everything into the core. See the [comparison table](/guide/#oxicloud-vs-nextcloud).
+
+### What hardware do I need?
+
+Minimum: 1 vCPU, 512 MB RAM, and a few GB of disk for PostgreSQL + file storage. OxiCloud runs comfortably on a Raspberry Pi 4.
+
+---
+
+## Installation
+
+### Which database is supported?
+
+PostgreSQL 13 or later. SQLite is not supported — PostgreSQL's ltree, array operations, and concurrent access are essential.
+
+### Can I use MySQL / MariaDB?
+
+Not currently. PostgreSQL is the only supported database.
+
+### How do I update?
+
+Pull the latest image and restart:
+
+```bash
+docker compose pull
+docker compose up -d
+```
+
+---
+
+## Features
+
+### Can I sync files from my desktop?
+
+WebDAV is built-in. You can mount OxiCloud in Windows Explorer, macOS Finder, or Linux file managers. A dedicated desktop sync client is on the roadmap.
+
+### Does CalDAV/CardDAV work with my phone?
+
+On Android, use [DAVx⁵](https://www.davx5.com/). On iOS, CalDAV and CardDAV work via the built-in Accounts settings.
+
+### Can I edit Office documents?
+
+Yes, via WOPI integration with Collabora Online or OnlyOffice. See [WOPI configuration](/config/wopi).
+
+### Is there end-to-end encryption?
+
+Not yet — it's on the roadmap. Files are stored unencrypted on the server (standard for self-hosted solutions that support server-side processing like thumbnails and search).
+
+---
+
+## Troubleshooting
+
+### I can't connect via WebDAV
+
+1. Check that the URL is `http(s)://host:8086/webdav/` (note the trailing slash)
+2. Ensure authentication is correct (HTTP Basic)
+3. Check server logs: `docker compose logs oxicloud`
+
+### Uploads fail for large files
+
+OxiCloud automatically switches to chunked upload for files over 200 MB. If you're behind a reverse proxy, ensure it allows large request bodies:
+
+```nginx
+client_max_body_size 0;  # unlimited
+proxy_read_timeout 600s;
+```
+
+### OIDC login doesn't redirect back
+
+Verify that `OXICLOUD_OIDC_REDIRECT_URI` matches exactly what's configured in your identity provider, and that `OXICLOUD_OIDC_FRONTEND_URL` points to your actual frontend URL.