feat: integrate TUI module and apply professional refactoring

include/tui.h

@@ -0,0 +1,29 @@
+#ifndef ASCII3D_TUI_H
+#define ASCII3D_TUI_H
+
+#include "renderer.h"
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Reconfigures standard input to be non-blocking and disables canonical mode.
+// This allows us to poll the keyboard gracefully in the render loop.
+int tui_init(void);
+
+// Restores terminal to its initial state to avoid leaving users with a broken
+// prompt.
+void tui_cleanup(void);
+
+// Processes pending keys and updates application state.
+// Standard typing appends to the text_buffer, while specific commands alter
+// settings. Returns non-zero when an exit is requested.
+int tui_process_input(RotationState *rotation, RenderSettings *settings,
+                      char *text_buffer, size_t max_text_len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif