Initial toni-sync CLI: sync local playlist folders to Kreativ-Tonies

- Config commands (config add/list/remove) to map local audio folders
  to Kreativ-Tonies via TonieCloud household/tonie ids
- tonies list command to look up household/tonie ids
- sync command: diff-based upload of new tracks, pruning of removed
  chapters, and reordering to match local file order (via tonie-api)
- Credentials resolved via env vars/CLI flags/prompt, never stored
- Unit tests for config persistence and sync planning/apply logic

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/test_config.py

@@ -0,0 +1,48 @@
+from pathlib import Path
+
+from toni_sync.config import AppConfig, ToniMapping, load_config, save_config
+
+
+def test_upsert_adds_new_mapping():
+    cfg = AppConfig()
+    m = ToniMapping(name="a", household_id="h1", tonie_id="t1", folder="/tmp/a")
+    cfg.upsert(m)
+    assert cfg.get("a") == m
+
+
+def test_upsert_replaces_existing_mapping():
+    cfg = AppConfig()
+    cfg.upsert(ToniMapping(name="a", household_id="h1", tonie_id="t1", folder="/tmp/a"))
+    updated = ToniMapping(name="a", household_id="h1", tonie_id="t2", folder="/tmp/a2")
+    cfg.upsert(updated)
+    assert len(cfg.mappings) == 1
+    assert cfg.get("a").tonie_id == "t2"
+
+
+def test_remove_returns_false_when_missing():
+    cfg = AppConfig()
+    assert cfg.remove("nope") is False
+
+
+def test_save_and_load_roundtrip(tmp_path: Path):
+    path = tmp_path / "config.yaml"
+    cfg = AppConfig()
+    cfg.upsert(
+        ToniMapping(
+            name="peppa",
+            household_id="h1",
+            tonie_id="t1",
+            folder="/tmp/peppa",
+            playlist_ref="https://example.com/playlist/1",
+        )
+    )
+    save_config(cfg, path)
+
+    loaded = load_config(path)
+    assert loaded.get("peppa").tonie_id == "t1"
+    assert loaded.get("peppa").playlist_ref == "https://example.com/playlist/1"
+
+
+def test_load_missing_file_returns_empty_config(tmp_path: Path):
+    cfg = load_config(tmp_path / "does-not-exist.yaml")
+    assert cfg.mappings == []