Add job processing system with streaming endpoint

Introduced a `processing` router to handle job streaming using server-sent events. Added `Jobs` and `JobStatus` models for managing job-related data, along with database creation logic. Updated the `sample` router to create new job entries during experiment creation.

backend/Dockerfile

@@ -3,6 +3,7 @@ FROM python:3.12-slim-bullseye
 
 # Set the working directory in the container
 WORKDIR /app
+RUN mkdir -p /app/backend/ssl
 
 # Install system dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
@@ -36,8 +37,6 @@ RUN pip install --no-cache-dir -r requirements.txt
 # Copy the rest of the application code
 COPY . /app
 
-RUN mkdir -p /app/backend/ssl
-
 # Expose the application port
 EXPOSE 8000