feat: add source channel context history configuration and original sent timestamp

db/models.py

@@ -16,6 +16,7 @@ class SourceChannel:
     username: Optional[str]
     title: Optional[str]
     category_id: Optional[int] = None
+    context_message_count: int = 0
     is_active: bool = True
     created_at: Optional[str] = None
 
@@ -65,6 +66,7 @@ class Post:
     review_message_id: Optional[int] = None
     scheduled_at: Optional[str] = None
     published_at: Optional[str] = None
+    source_created_at: Optional[str] = None
     created_at: Optional[str] = None
 
 @dataclass