Switch repo to English, add i18n with EN/DE language files and first-start language selection

- in-game texts moved to lang/en.lang and lang/de.lang (key = text, placeholders)
- game logic emits message keys + args, translated at display time
- localStorage access via own miniquad JS plugin (www/dc_plugin.js)
- code comments, DESIGN.md, CREDITS.md translated; README.md added

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

CREDITS.md

@@ -1,9 +1,9 @@
 # Credits
 
-## Schrift: DINOBYTE bitmap font
-- Autor: **mby** – https://mby.itch.io/dinobyte
-- Lizenz: **Creative Commons Attribution 4.0 International (CC BY 4.0)** – https://creativecommons.org/licenses/by/4.0/
-- Datei: `assets/dbyte_1x.png` (unverändert). Im Spiel wird sie ganzzahlig skaliert und eingefärbt dargestellt.
+## Font: DINOBYTE bitmap font
+- Author: **mby** – https://mby.itch.io/dinobyte
+- License: **Creative Commons Attribution 4.0 International (CC BY 4.0)** – https://creativecommons.org/licenses/by/4.0/
+- File: `assets/dbyte_1x.png` (unmodified). In the game it is scaled by integer factors and tinted. The swapped glyphs ö/ò are corrected in the character mapping, not in the file.
 
-## Alles andere
-Code, prozedurale Grafiken und Spieldesign: DungeonCraft-Projekt.
+## Everything else
+Code, procedural graphics and game design: the DungeonCraft project.