fix(backend): bundle unidic-lite for misaki Japanese G2P (#514)

fugashi (pulled in by misaki[ja]) needs a MeCab dictionary at runtime.
The `unidic` package that ships today contains no data — it relies on
`python -m unidic download` (~526MB), which isn't run by `just setup`
and won't survive PyInstaller freezing.

Switch to `unidic-lite`, which bundles a MeCab-compatible dict inside
the wheel (~50MB). Collect its data files in build_binary.py so frozen
builds also pick up the dicdir. Same failure mode and same fix shape as
the existing en_core_web_sm pre-install.

backend/build_binary.py

@@ -287,6 +287,12 @@ def build_server(cuda=False):
             "en_core_web_sm",
             "--hidden-import",
             "en_core_web_sm",
+            # unidic-lite ships the MeCab dictionary used by fugashi (pulled in
+            # by misaki[ja]). The dict lives in unidic_lite/dicdir/ and is
+            # discovered via the package's DICDIR constant, so the data files
+            # must be collected or Japanese Kokoro voices crash at runtime.
+            "--collect-all",
+            "unidic_lite",
             "--hidden-import",
             "loguru",
         ]