Support Custom OpenAI-compatible endpoints for speech-to-text transcription (Fixes #136)

[AdamMagued]

Summary

Resolves #136.

Enables configured Custom OpenAI-compatible endpoints (such as OmniRoute, LocalAI, vLLM, etc.) to be selectable and used for speech-to-text (transcription) both in global dictation / recording and in dedicated transcription tools.

Key Changes

1. Transcription Provider Options:

   • Added CUSTOM_OPENAI to TranscriptionProvider in consts.py (custom_openai).
   • Exposed Custom OpenAI in the settings dialog transcription provider choice list.
   • Added Custom OpenAI transcription account dropdown to the Provider account mapping group in the settings dialog.
   • Updated configspec.py with customOpenAITranscriptionAccountId and customOpenAITranscriptionModel.

2. Transcription Routing and Endpoint Wiring:

   • Implemented _transcribe_custom_openai in RecordThread and updated transcribe_audio_file.
   • Wired transcription requests to call /audio/transcriptions on the configured custom base URL using the configured API credentials.
   • Added helper functions in transcription.py (list_transcription_providers, get_transcription_provider_choices, resolve_transcription_endpoint, and enhanced provider normalization).
   • Updated conversation_dialog.py _resolveDictationConfig to support Custom OpenAI transcription account mapping and model resolution.

3. Tools Menu and Dedicated Dialog Integration:

   • Added ToolId.CUSTOM_OPENAI_TRANSCRIPTION to TOOLS_REGISTRY and included Provider.CustomOpenAI in _GROUP_ORDER in toolsmenu.py.
   • Added CustomOpenAITranscriptionToolDialog and updated OpenAITranscriptionToolDialog to display and configure accounts from Custom OpenAI.
   • Added TOOL_CUSTOM_OPENAI_TRANSCRIPTION to ConversationFormat and mapped it in conversations_manager_dialog.py.

4. Robustness & Edge Cases:

   • Normalized custom base URLs to strip trailing slashes, preventing double-slash paths (e.g. //audio/transcriptions).
   • Allowed CustomOpenAI user endpoints with optional API keys so local servers without auth are supported without validation errors.
   • Ensured script_toggleRecording and script_askQuestion do not prematurely block recording when Custom OpenAI or local transcription is configured.

5. Testing:

   • Added 22 unit tests in tests/test_custom_transcription.py covering provider listing, custom endpoint resolution, request wiring, URL normalization, tools menu registry, and dictation resolution.

Verification

• All 22 unit tests pass (pytest -v).
• Syntax validation passes across all modified modules.