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/reflector/processors/transcript_translator.py

@@ -1,9 +1,5 @@
-import httpx
-
 from reflector.processors.base import Processor
-from reflector.processors.types import Transcript, TranslationLanguages
-from reflector.settings import settings
-from reflector.utils.retry import retry
+from reflector.processors.types import Transcript
 
 
 class TranscriptTranslatorProcessor(Processor):
@@ -17,56 +13,23 @@ class TranscriptTranslatorProcessor(Processor):
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
         self.transcript = None
-        self.translate_url = settings.TRANSLATE_URL
-        self.timeout = settings.TRANSLATE_TIMEOUT
-        self.headers = {"Authorization": f"Bearer {settings.TRANSCRIPT_MODAL_API_KEY}"}
 
     async def _push(self, data: Transcript):
         self.transcript = data
         await self.flush()
 
-    async def get_translation(self, text: str) -> str | None:
-        # FIXME this should be a processor after, as each user may want
-        # different languages
-
-        source_language = self.get_pref("audio:source_language", "en")
-        target_language = self.get_pref("audio:target_language", "en")
-        if source_language == target_language:
-            return
-
-        languages = TranslationLanguages()
-        # Only way to set the target should be the UI element like dropdown.
-        # Hence, this assert should never fail.
-        assert languages.is_supported(target_language)
-        self.logger.debug(f"Try to translate {text=}")
-        json_payload = {
-            "text": text,
-            "source_language": source_language,
-            "target_language": target_language,
-        }
-
-        async with httpx.AsyncClient() as client:
-            response = await retry(client.post)(
-                self.translate_url + "/translate",
-                headers=self.headers,
-                params=json_payload,
-                timeout=self.timeout,
-                follow_redirects=True,
-                logger=self.logger,
-            )
-            response.raise_for_status()
-            result = response.json()["text"]
-
-            # Sanity check for translation status in the result
-            if target_language in result:
-                translation = result[target_language]
-            self.logger.debug(f"Translation response: {text=}, {translation=}")
-        return translation
+    async def _translate(self, text: str) -> str | None:
+        raise NotImplementedError
 
     async def _flush(self):
         if not self.transcript:
             return
-        self.transcript.translation = await self.get_translation(
-            text=self.transcript.text
-        )
+
+        source_language = self.get_pref("audio:source_language", "en")
+        target_language = self.get_pref("audio:target_language", "en")
+        if source_language == target_language:
+            self.transcript.translation = None
+        else:
+            self.transcript.translation = await self._translate(self.transcript.text)
+
         await self.emit(self.transcript)