docs(readme): add per-OS desktop download table

Replaces the single generic releases-page link with direct downloads
for Windows (.exe), Linux (AppImage/.deb/.pkg.tar.zst), plus a note on
the webkit2gtk/GStreamer WebRTC dependency needed for calls to work.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -129,7 +129,16 @@ Lotus Chat has a desktop app for Windows, macOS, and Linux. It wraps the same we
 
 ### Download
 
-Download the latest release from the [Releases page on code.lotusguild.org](https://code.lotusguild.org).
+Operating System | Download
+---|---
+Windows | [Get the installer (.exe)](https://code.lotusguild.org/LotusGuild/cinny-desktop/releases/download/latest/LotusChat-x86_64-setup.exe)
+Linux (AppImage, any distro) | [Get the AppImage](https://code.lotusguild.org/LotusGuild/cinny-desktop/releases/download/latest/LotusChat-x86_64.AppImage)
+Linux (Debian/Ubuntu) | [Get the .deb](https://code.lotusguild.org/LotusGuild/cinny-desktop/releases/download/latest/LotusChat-x86_64.deb)
+Linux (Arch/CachyOS/EndeavourOS) | [Get the .pkg.tar.zst](https://code.lotusguild.org/LotusGuild/cinny-desktop/releases/download/latest/LotusChat-x86_64.pkg.tar.zst) — install with `pacman -U LotusChat-x86_64.pkg.tar.zst`
+
+All Linux builds need `webkit2gtk-4.1` and, for calls to work, GStreamer's `good`/`bad`/`ugly`/`libav` plugin sets (the pacman package pulls these in automatically; on the AppImage/.deb, install them via your package manager if joining a call shows "browser does not support WebRTC").
+
+See the full [Releases page on code.lotusguild.org](https://code.lotusguild.org/LotusGuild/cinny-desktop/releases) for signatures and older builds.
 
 ### SmartScreen Warning (Windows)