docs: link the wiki install/update tutorials, add Updating section

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

doc/usage.md

@@ -226,6 +226,19 @@ Pick a creator, type a query and press **Search** to run the query through
 Floatplane's search API and see the matching videos (date, sub-channel,
 title, length). This is a diagnostic tool; it does not change anything.
 
+## Updating
+
+- **Automatic**: Jellyfin's nightly *Update Plugins* task installs newer versions from
+  the repository (the plugin ships with `autoUpdate` on). When *My Plugins* shows
+  **Status Restart**, restart Jellyfin.
+- **Manual through the catalogue**: Dashboard → Plugins → Catalog → Channels →
+  Floatplane → Install (newest revision) → restart.
+- **Script**: `install.sh` from the release (see Install above) replaces the plugin
+  folder and restarts Jellyfin.
+
+Step-by-step with screenshots: [Update tutorial](https://gitea.brasse-pc.eu/brasse/jellyfin-plugin-floatplane/wiki/Update)
+in the wiki (and the [Install tutorial](https://gitea.brasse-pc.eu/brasse/jellyfin-plugin-floatplane/wiki/Install)).
+
 ## Scheduled task
 
 The plugin registers **Refresh Floatplane catalogue** under **Dashboard →