feat(io): SwingIO 4-region layout, JTextPane styling, bundled font loader

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Semesterprojekt/src/main/resources/fonts/README.md

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+# Bundled GUI font
+
+Drop a TrueType font here named `game.ttf` to use it in the Swing GUI
+(`SwingIO`). It is loaded via `Font.createFont` and registered at runtime —
+no installation on the player's machine required.
+
+- A monospaced font is recommended (the UI assumes fixed width for frames).
+- A Nerd Font variant additionally provides icon glyphs.
+- Check the font's licence before committing the `.ttf`.
+
+If no `game.ttf` is present, `SwingIO` falls back to the logical
+`Font.MONOSPACED`, so the game still runs.