feat: issue relations (link/unlink parent-child, list children)

app/main.py

@@ -693,3 +693,38 @@ def list_activity(
     if user_id:
         query = query.filter(ActivityLog.user_id == user_id)
     return query.order_by(ActivityLog.created_at.desc()).limit(limit).all()
+
+
+
+# ============ Issue Relations ============
+
+class IssueRelation(PydanticBaseModel):
+    parent_id: int
+    child_id: int
+
+@app.post("/issues/link")
+def link_issues(rel: IssueRelation, db: Session = Depends(get_db)):
+    parent = db.query(models.Issue).filter(models.Issue.id == rel.parent_id).first()
+    child = db.query(models.Issue).filter(models.Issue.id == rel.child_id).first()
+    if not parent or not child:
+        raise HTTPException(status_code=404, detail="Issue not found")
+    if rel.parent_id == rel.child_id:
+        raise HTTPException(status_code=400, detail="Cannot link issue to itself")
+    child.depends_on_id = rel.parent_id
+    db.commit()
+    return {"parent_id": rel.parent_id, "child_id": rel.child_id, "status": "linked"}
+
+
+@app.delete("/issues/link")
+def unlink_issues(child_id: int, db: Session = Depends(get_db)):
+    child = db.query(models.Issue).filter(models.Issue.id == child_id).first()
+    if not child:
+        raise HTTPException(status_code=404, detail="Issue not found")
+    child.depends_on_id = None
+    db.commit()
+    return {"child_id": child_id, "status": "unlinked"}
+
+
+@app.get("/issues/{issue_id}/children", response_model=List[schemas.IssueResponse])
+def get_children(issue_id: int, db: Session = Depends(get_db)):
+    return db.query(models.Issue).filter(models.Issue.depends_on_id == issue_id).all()