TTS cleanup & update Rails to 7.0.5

[lumpidu]

Upgrade Ruby to 3.2.2 & Rails to 7.0.5

Revamp TTS service

• use class instance variables instead of class variables (style)
• download voice info at startup/initialization time and prefill TtsService::supported_voices array
• use connection pool instead of always allocating a new connection, limit pool to 10 connections with timout of 5 secs
• add handling of rate limiting (429) and retry with backoff
• relattion of tts_audio attachment changed from has_one_attached => has_many_attached
• use ActiveStorage::Blob for creating download URL
• cleanup job now is correctly passed a message id instead of a message Ruby object, which cannot work on real job queues like e.g. Sidekiq
• refactor out some methods & cleanup