feat: implement service-specific Modal API keys with auto processor pattern (#528)

* fix: refactor modal API key configuration for better separation of concerns

- Split generic MODAL_API_KEY into service-specific keys:
  - TRANSCRIPT_API_KEY for transcription service
  - DIARIZATION_API_KEY for diarization service
  - TRANSLATE_API_KEY for translation service
- Remove deprecated *_MODAL_API_KEY settings
- Add proper validation to ensure URLs are set when using modal processors
- Update README with new configuration format

BREAKING CHANGE: Configuration keys have changed. Update your .env file:
- TRANSCRIPT_MODAL_API_KEY → TRANSCRIPT_API_KEY
- LLM_MODAL_API_KEY → (removed, use TRANSCRIPT_API_KEY)
- Add DIARIZATION_API_KEY and TRANSLATE_API_KEY if using those services

* fix: update Modal backend configuration to use service-specific API keys

- Changed from generic MODAL_API_KEY to service-specific keys:
  - TRANSCRIPT_MODAL_API_KEY for transcription
  - DIARIZATION_MODAL_API_KEY for diarization
  - TRANSLATION_MODAL_API_KEY for translation
- Updated audio_transcript_modal.py and audio_diarization_modal.py to use modal_api_key parameter
- Updated documentation in README.md, CLAUDE.md, and env.example

* feat: implement auto/modal pattern for translation processor

- Created TranscriptTranslatorAutoProcessor following the same pattern as transcript/diarization
- Created TranscriptTranslatorModalProcessor with TRANSLATION_MODAL_API_KEY support
- Added TRANSLATION_BACKEND setting (defaults to "modal")
- Updated all imports to use TranscriptTranslatorAutoProcessor instead of TranscriptTranslatorProcessor
- Updated env.example with TRANSLATION_BACKEND and TRANSLATION_MODAL_API_KEY
- Updated test to expect TranscriptTranslatorModalProcessor name
- All tests passing

* refactor: simplify transcript_translator base class to match other processors

- Moved all implementation from base class to modal processor
- Base class now only defines abstract _translate method
- Follows the same minimal pattern as audio_diarization and audio_transcript base classes
- Updated test mock to use _translate instead of get_translation
- All tests passing

* chore: clean up settings and improve type annotations

- Remove deprecated generic API key variables from settings
- Add comments to group Modal-specific settings
- Improve type annotations for modal_api_key parameters

* fix: typing

* fix: passing key to openai

* test: fix rtc test failing due to change on transcript

It also correctly setup database from sqlite, in case our configuration
is setup to postgres.

* ci: deactivate translation backend by default

* test: fix modal->mock

* refactor: implementing igor review, mock to passthrough

server/uv.lock

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 ]
 
+[[package]]
+name = "pytest-env"
+version = "1.1.5"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/1f/31/27f28431a16b83cab7a636dce59cf397517807d247caa38ee67d65e71ef8/pytest_env-1.1.5.tar.gz", hash = "sha256:91209840aa0e43385073ac464a554ad2947cc2fd663a9debf88d03b01e0cc1cf", size = 8911, upload-time = "2024-09-17T22:39:18.566Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/de/b8/87cfb16045c9d4092cfcf526135d73b88101aac83bc1adcf82dfb5fd3833/pytest_env-1.1.5-py3-none-any.whl", hash = "sha256:ce90cf8772878515c24b31cd97c7fa1f4481cd68d588419fd45f10ecaee6bc30", size = 6141, upload-time = "2024-09-17T22:39:16.942Z" },
+]
+
 [[package]]
 name = "pytest-httpx"
 version = "0.34.0"
@@ -2636,6 +2648,7 @@ dependencies = [
     { name = "protobuf" },
     { name = "psycopg2-binary" },
     { name = "pydantic-settings" },
+    { name = "pytest-env" },
     { name = "python-jose", extra = ["cryptography"] },
     { name = "python-multipart" },
     { name = "redis" },
@@ -2699,6 +2712,7 @@ requires-dist = [
     { name = "protobuf", specifier = ">=4.24.3" },
     { name = "psycopg2-binary", specifier = ">=2.9.10" },
     { name = "pydantic-settings", specifier = ">=2.0.2" },
+    { name = "pytest-env", specifier = ">=1.1.5" },
     { name = "python-jose", extras = ["cryptography"], specifier = ">=3.3.0" },
     { name = "python-multipart", specifier = ">=0.0.6" },
     { name = "redis", specifier = ">=5.0.1" },