feat: add is_chat field to board memory and task_id to approvals, update pagination and response models

backend/app/models/board_memory.py

@@ -16,5 +16,6 @@ class BoardMemory(SQLModel, table=True):
     board_id: UUID = Field(foreign_key="boards.id", index=True)
     content: str
     tags: list[str] | None = Field(default=None, sa_column=Column(JSON))
+    is_chat: bool = Field(default=False, index=True)
     source: str | None = None
     created_at: datetime = Field(default_factory=utcnow)