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/app/models.py

@@ -7,10 +7,13 @@ from sqlalchemy import (
     JSON,
     DateTime,
     Boolean,
+    Enum,
+    func,
 )
 from sqlalchemy.orm import relationship
 from .database import Base
 from datetime import datetime
+import enum
 
 
 class Shipment(Base):
@@ -303,3 +306,20 @@ class Results(Base):
 #    total_refl: int
 #    unique_refl: int
 #    #comments: Optional[constr(max_length=200)] = None
+
+
+class JobStatus(str, enum.Enum):
+    TODO = "todo"
+    SUBMITTED = "submitted"
+    DONE = "done"
+
+
+class Jobs(Base):
+    __tablename__ = "jobs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    experiment_parameters_id = Column(Integer, nullable=False)
+    status = Column(Enum(JobStatus), default=JobStatus.TODO, nullable=False)
+    parameters = Column(JSON, nullable=False)
+    created_at = Column(DateTime, server_default=func.now())
+    updated_at = Column(DateTime, onupdate=func.now())