fix: move translation file I/O off the event loop

[r0bb10]

Preload translation files into cache via hass.async_add_executor_job before building the dashboard, so _t() calls during dashboard config construction are pure dict lookups with zero blocking I/O.

• Add _async_preload_translations() that resolves language and loads both the target and English translations via the async executor
• Updated _build_dashboard_config to accept pre-resolved lang param instead of doing its own I/O

[andbad]

Hi, thanks for the contribution — the approach is clean and the async preload is the right direction.

One thing to clarify before merging: the current codebase calls _STRINGS_CACHE.clear() at the start of _build_dashboard_config to ensure language changes are picked up on every rebuild. Your PR removes that line without replacing it.

Could you check whether _load_strings skips loading if the key is already present in _STRINGS_CACHE? If it does, a language change made by the user would not take effect until HA restarts.

If that's the case, adding _STRINGS_CACHE.clear() at the top of _async_preload_translations before the load loop would fix it.

By(t)e