Adds 4 fr-CA + 3 fr-FR Edge neural voices so francophone users can use
the Edge TTS engine instead of receiving HTTP 400 "invalid voice" on
every utterance. Pure superset of the existing allowlist; no validation
or rate-limit behavior changes.
Tests mirror the test_issue2931 in-process / mocked-edge_tts pattern:
each new voice is parametrized through _handle_tts and asserted to
reach synthesis (HTTP 200); fr-BE-CharlineNeural (real Edge voice
but intentionally unlisted) is asserted to still 400.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
