New voices and refreshed listening setup

We've added a new tier of higher-quality voices to listening and conjugation practice, and refreshed the voice picker.

Voices are now grouped into three quality tiers, shown as a tag next to each voice name:

  • v3: our newest, highest-quality voices, marked with a red NEW badge.
  • v2: high-quality standard voices.
  • v1: classic voices.

The picker sorts v3 first and shows a flag next to each dialect.

On the listening page, Filter by topic and Filter by tense are now toggles. Flip one off and its selector hides.