Add backend support for the typing game: curriculum, progress, and reward unlocks

Moves the typing app's lesson plan and progress from client-side YAML/localStorage
into the backend, and adds a reward system that ties passing a lesson to unlocking
part of the music library. Lock state is always recomputed live from curriculum x
progress x the live library, never persisted separately.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

python-backend/musicmouse/config.py

@@ -43,6 +43,7 @@ __all__ = [
     "LircConfig",
     "MqttConfig",
     "RemoteSlotConfig",
+    "TippenConfig",
     "WebConfig",
     "format_validation_error",
     "load_config",
@@ -116,14 +117,19 @@ class FigureColors(_Strict):
         return data
 
 
-def _resolve_folder(folder: Path, info: ValidationInfo, *, must_exist: bool) -> Path:
+def _resolve_folder(
+    folder: Path, info: ValidationInfo, *, must_exist: bool, kind: Literal["dir", "file"] = "dir"
+) -> Path:
     """Make a configured path absolute against the config file, and optionally check it."""
     context = info.context or {}
     base = context.get("config_dir")
     if base is not None and not folder.is_absolute():
         folder = (Path(base) / folder).resolve()
-    if must_exist and context.get("check_paths", True) and not folder.is_dir():
-        raise ValueError(f"no such directory: {folder}")
+    if must_exist and context.get("check_paths", True):
+        exists = folder.is_file() if kind == "file" else folder.is_dir()
+        if not exists:
+            noun = "file" if kind == "file" else "directory"
+            raise ValueError(f"no such {noun}: {folder}")
     return folder
 
 
@@ -227,6 +233,29 @@ class HaConfig(_Strict):
         return self
 
 
+class TippenConfig(_Strict):
+    """The typing game. Omit the whole section to run without it.
+
+    The curriculum is content, not device settings, so it lives in its own file
+    (``curriculum_file``) rather than inline here - see ``tippen-curriculum.yml.example``.
+    ``progress_file`` is written by the app itself, not hand-edited, and defaults to a
+    name next to ``config.yml`` if not given a folder of its own.
+    """
+
+    curriculum_file: Path
+    progress_file: Path = Path("tippen-progress.json")
+
+    @field_validator("curriculum_file")
+    @classmethod
+    def _resolve_curriculum_file(cls, path: Path, info: ValidationInfo) -> Path:
+        return _resolve_folder(path, info, must_exist=True, kind="file")
+
+    @field_validator("progress_file")
+    @classmethod
+    def _resolve_progress_file(cls, path: Path, info: ValidationInfo) -> Path:
+        return _resolve_folder(path, info, must_exist=False, kind="file")
+
+
 class GeneralConfig(_Strict):
     library: LibraryConfig
 
@@ -244,6 +273,7 @@ class GeneralConfig(_Strict):
     web: WebConfig | None = None
     ha: HaConfig | None = None
     lirc: LircConfig | None = None
+    tippen: TippenConfig | None = None
 
     min_volume: int = Field(default=0, ge=0, le=200)
     max_volume: int = Field(default=100, ge=0, le=200)