feat(comments): add reply threading + UI

backend/alembic/versions/9d3d9b9c1a23_add_reply_to_task_comments.py

@@ -0,0 +1,32 @@
+"""add reply_to_comment_id to task_comments
+
+Revision ID: 9d3d9b9c1a23
+Revises: 157587037601
+Create Date: 2026-02-02 08:15:00.000000
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = "9d3d9b9c1a23"
+down_revision = "157587037601"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("task_comments", sa.Column("reply_to_comment_id", sa.Integer(), nullable=True))
+    op.create_foreign_key(
+        "fk_task_comments_reply_to_comment_id",
+        "task_comments",
+        "task_comments",
+        ["reply_to_comment_id"],
+        ["id"],
+    )
+
+
+def downgrade() -> None:
+    op.drop_constraint("fk_task_comments_reply_to_comment_id", "task_comments", type_="foreignkey")
+    op.drop_column("task_comments", "reply_to_comment_id")

backend/app/api/work.py

@@ -89,6 +89,12 @@ def create_task_comment(payload: TaskCommentCreate, session: Session = Depends(g
     if payload.author_employee_id is None:
         payload = TaskCommentCreate(**{**payload.model_dump(), "author_employee_id": actor_employee_id})
     c = TaskComment(**payload.model_dump())
+
+    # Validate reply target (must exist + belong to same task)
+    if c.reply_to_comment_id is not None:
+        parent = session.get(TaskComment, c.reply_to_comment_id)
+        if parent is None or parent.task_id != c.task_id:
+            raise HTTPException(status_code=400, detail="Invalid reply_to_comment_id")
     session.add(c)
     session.commit()
     session.refresh(c)

backend/app/models/work.py

@@ -30,5 +30,9 @@ class TaskComment(SQLModel, table=True):
     id: int | None = Field(default=None, primary_key=True)
     task_id: int = Field(foreign_key="tasks.id", index=True)
     author_employee_id: int | None = Field(default=None, foreign_key="employees.id")
+
+    # Optional reply threading
+    reply_to_comment_id: int | None = Field(default=None, foreign_key="task_comments.id")
+
     body: str
     created_at: datetime = Field(default_factory=datetime.utcnow)

backend/app/schemas/work.py

@@ -24,4 +24,5 @@ class TaskUpdate(SQLModel):
 class TaskCommentCreate(SQLModel):
     task_id: int
     author_employee_id: int | None = None
+    reply_to_comment_id: int | None = None
     body: str