Add Oracle Cloud AI Speech provider

[LubuSeb]

Summary

Adds an Oracle Cloud AI Speech transcription provider behind --api oracle.

The provider:

• uploads Sapat's generated MP3 to OCI Object Storage
• creates an Oracle Cloud AI Speech transcription job
• polls the transcription task and fetches the full task before reading output
• reads transcript JSON from the configured output bucket
• supports Oracle locale normalization and explicit configuration errors
• keeps OCI support as an optional sapat[oracle] dependency

Validation

• python -m unittest discover -s tests -v
• python -m compileall src tests
• sapat --help
• git diff --check

[nibzard]

Thank you for this contribution! Your implementation was reviewed as part of a batch review of all incoming provider PRs.

We've decided to take a different approach: instead of merging individual provider PRs (which all targeted a different code architecture than what exists on main), we've refactored the entire codebase into a proper provider plugin architecture with auto-discovery and shared mixins. Your provider's API integration patterns were used as reference when building the Oracle Cloud AI Speech provider in the new architecture.

The refactor is on branch feat/provider-plugin-architecture and includes 29 providers, 176 tests, and a clean plugin system. We appreciate your contribution — it helped shape the final design. Closing this in favor of the unified approach.