fix(flatpak): install GL runtime matching nvidia driver

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

hosts/common/features/flatpak.nix

@@ -1,4 +1,10 @@
-{ inputs, lib, ... }:
+{ config, inputs, lib, ... }:
+let
+  # The Flatpak GL runtime must match the host NVIDIA driver exactly, or apps
+  # fail with "Unable to create a valid OpenGL context".
+  nvidiaGl = "org.freedesktop.Platform.GL.nvidia-" + builtins.replaceStrings [ "." ] [ "-" ] config.hardware.nvidia.package.version;
+in
+
 {
   imports = [ inputs.nix-flatpak.nixosModules.nix-flatpak ];
 
@@ -15,6 +21,9 @@
     ];
 
     packages = [
+      # Tracks the driver version, so it follows nvidia bumps automatically.
+      { appId = nvidiaGl; origin = "flathub"; }
+
       # PrusaSlicer 3.x. As of 3.0 Prusa ships no Linux binary at all — Flathub
       # is the only channel, and the alphas live in flathub-beta. Runs alongside
       # pkgs.prusa-slicer (2.9.x, in home/common/programs/3d.nix): 3.x keeps its