feat: enhance authentication and publication download tracking

- Added JWT authentication support with configurable secret and expiration.
- Introduced optional API key validation for endpoints.
- Implemented tracking of publication downloads by researchers, storing records in a new PublicationDownload model.
- Updated export endpoints to conditionally register downloads based on user authentication.
- Enhanced researcher search response to indicate if publications were downloaded by the current user.
- Updated environment configuration to include new JWT settings.

backend/app/schema/publication.py

@@ -25,6 +25,5 @@ class PublicationSchema(BaseModel):
     hash_fingerprint: str | None = None
     last_modified: datetime | None = None
     status: str | None = None
-
-    class Config:
-        from_attributes = True
+    downloaded_by_me: bool | None = None
+    model_config = {"from_attributes": True}