feat(i18n): proper multilingual input

Use fcitx5 to switch between different inputs. Installed mozc-ut for
Japanese input with the bepo layout, as well as fcitx5-chinese to load
table-defined layouts for the IPA/X-SAMPA input method.

Currently, mozc_server and fcitx5 need to be launched by the
compositor (only Hyprland for now), auto-launching from module options
needs to be implemented in the future.

hosts/gampo/configuration.nix

@@ -41,6 +41,7 @@
       };
       sound.enable = true;
     };
+    i18n.input.enable = true;
     misc.keymap = "fr-bepo";
     networking = {
       hostname = "gampo";