Add tests, fix offset logic, and bump dependencies

- Introduce a comprehensive test suite (cli, app, board, tasks, audio)
  and a
  new TESTING.md document describing test execution.
- Correct vertical offset calculation in `BoardState` to use saturating
  subtraction and ceiling division.
- Clamp initial `Offset` values to the provided maximum in
  `Offset::new`.
- Export `load_audio` from the audio thread module and switch to
  `LoopedDecoder` for proper OGG looping.
- Update several crate versions: clap, ratatui, log, rodio, and
  bitflags.

tests/audio.rs

@@ -0,0 +1,19 @@
+use rodio::Decoder;
+use std::{
+    fs::read,
+    io::{BufReader, Cursor},
+};
+use war_in_tunnels::app::threads::{SoundrackParts, Soundtrack, load_audio};
+
+#[test]
+fn audio_repeats_after_end_of_file() {
+    let data = read("soundtracks/default/calm.ogg").unwrap();
+    let sample_count = Decoder::new(BufReader::new(Cursor::new(data)))
+        .unwrap()
+        .count();
+    assert!(sample_count > 0);
+
+    let mut source = load_audio(&Soundtrack::Default, &SoundrackParts::Calm);
+    assert_eq!(source.by_ref().take(sample_count).count(), sample_count);
+    assert_eq!(source.take(1024).count(), 1024);
+}