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>

src/toni_sync/config.py

@@ -0,0 +1,72 @@
+"""Configuration handling for toni-sync.
+
+Stores the mapping between local audio folders (e.g. exported Deezer
+playlists) and Kreativ-Tonies in a simple YAML file. Credentials for the
+TonieCloud account are NEVER stored here - they are provided via
+environment variables or interactive prompt (see client.py).
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+import yaml
+from pydantic import BaseModel, Field
+
+DEFAULT_CONFIG_PATH = Path(
+    os.environ.get("TONI_SYNC_CONFIG", str(Path.home() / ".config" / "toni-sync" / "config.yaml"))
+)
+
+
+class ToniMapping(BaseModel):
+    """Mapping of a local folder to a Kreativ-Tonie."""
+
+    name: str  # unique friendly identifier used on the CLI, e.g. "peppa-wutz"
+    household_id: str
+    tonie_id: str
+    tonie_name: str | None = None  # informational, kept in sync on config add/list
+    folder: str  # local path containing the audio files for this tonie
+    playlist_ref: str | None = None  # informational, e.g. deezer playlist URL/ID
+    prune: bool = True  # remove chapters on the tonie that no longer exist locally
+
+    @property
+    def folder_path(self) -> Path:
+        return Path(self.folder).expanduser()
+
+
+class AppConfig(BaseModel):
+    """The full toni-sync configuration."""
+
+    mappings: list[ToniMapping] = Field(default_factory=list)
+
+    def get(self, name: str) -> ToniMapping | None:
+        return next((m for m in self.mappings if m.name == name), None)
+
+    def upsert(self, mapping: ToniMapping) -> None:
+        for i, existing in enumerate(self.mappings):
+            if existing.name == mapping.name:
+                self.mappings[i] = mapping
+                return
+        self.mappings.append(mapping)
+
+    def remove(self, name: str) -> bool:
+        before = len(self.mappings)
+        self.mappings = [m for m in self.mappings if m.name != name]
+        return len(self.mappings) != before
+
+
+def load_config(path: Path | None = None) -> AppConfig:
+    path = path or DEFAULT_CONFIG_PATH
+    if not path.exists():
+        return AppConfig()
+    with path.open("r", encoding="utf-8") as fh:
+        raw = yaml.safe_load(fh) or {}
+    return AppConfig(**raw)
+
+
+def save_config(config: AppConfig, path: Path | None = None) -> None:
+    path = path or DEFAULT_CONFIG_PATH
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("w", encoding="utf-8") as fh:
+        yaml.safe_dump(config.model_dump(), fh, allow_unicode=True, sort_keys=False)