feature: localization (#32)

* build: add nlohmann/json library

* build(deps): add harfbuzz dependency

* feat(cmake): add guard to reject macOS builds

* feat(font): add HarfBuzz shaping and replace font with unifont

* feat(localization): add i18n support with en_US and zh_CN translations

Implement Localization class to load JSON translation files. Replace hardcoded strings in UI with translation keys and update sliders/combo buttons to use dynamic text.

* feat(localization): detect system locale for language default

* feat(settings): add language selection option with restart notification

* fix: use vckpg to add freetype on windows

assets/lang/en_US.json

@@ -0,0 +1,34 @@
+{
+    "menu.settings": "Settings",
+    "menu.main.host_game": "Host Game",
+    "menu.main.join_game": "Join Game",
+    "menu.main.credits": "Credits",
+    "menu.main.quit": "Quit",
+    "menu.main.player_name": "Player: {name}",
+    "menu.main.cubed_version": "Cubed: {version}",
+    "menu.pause.pause_menu": "Pause Menu",
+    "menu.pause.back_to_game": "Back To Game",
+    "menu.pause.return_to_main_menu": "Return to Menu",
+    "button.done": "Done",
+    "button.return": "Return",
+    "settings.title": "Settings",
+    "settings.fov": "Fov: {fov}",
+    "settings.mouse_sensitivity": "Sensitivity: {sensitivity}",
+    "settings.distance": "Distance: {distance}",
+    "settings.music_volume": "Music: {music}",
+    "settings.sfx_volume": "SFX: {sfx}",
+    "settings.fullscreen": "fullscreen: {state}",
+    "settings.aniso": "Aniso: {aniso}",
+    "settings.vsync": "V-Sync: {state}",
+    "settings.language": "Language: {lang}",
+    "settings.restart_game_info": "You need to restart the game to apply this changes.",
+    "common.on": "on",
+    "common.off": "off",
+    "hostgame.create_a_new_world": "Create A New World",
+    "hostgame.world_seed": "World Seed",
+    "hostgame.port": "Port",
+    "hostgame.create_world": "Create World",
+    "joingame.join_a_world": "Join A World",
+    "joingame.server_ip": "Server Ip",
+    "joingame.join_world": "Join World"
+}