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/guide/trash.md

@@ -0,0 +1,27 @@
+# Trash & Recycle Bin
+
+OxiCloud provides a trash system that soft-deletes files and folders, allowing users to restore or permanently remove them.
+
+## How It Works
+
+1. When a file or folder is deleted, it's **soft-deleted** — a flag (`is_trashed`) is set and a `trashed_at` timestamp is recorded
+2. Trashed items are hidden from normal file listings but remain on disk and in the database
+3. Users can browse the trash, restore items, or permanently delete them
+4. Items older than the retention period (default: **30 days**) are automatically purged
+
+## API Endpoints
+
+| Method | Endpoint | Description |
+|--------|----------|-------------|
+| GET | `/api/trash` | List trashed items |
+| POST | `/api/trash/restore/{id}` | Restore a trashed item |
+| DELETE | `/api/trash/{id}` | Permanently delete |
+| DELETE | `/api/trash/empty` | Empty the entire trash |
+
+## Deduplication Interaction
+
+Permanent deletion decrements the blob reference count. If no other file points to the same blob, the blob is removed from disk.
+
+## Feature Flag
+
+Trash can be disabled via `OXICLOUD_ENABLE_TRASH=false`. When disabled, deletions are permanent.