feat: add deleted-user builtin and safe user deletion

- Add deleted-user as a built-in account (no permissions, cannot log in)
  created during init_wizard, protected from deletion like acc-mgr
- On user delete, reassign all foreign key references to deleted-user
  then delete the original user, instead of failing on IntegrityError
- API keys, notifications, and project memberships are deleted outright
  since they're meaningless without the real user

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/api/routers/users.py

@@ -9,6 +9,7 @@ from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_user, get_current_user_or_apikey, get_password_hash
 from app.core.config import get_db
+from app.init_wizard import DELETED_USER_USERNAME
 from app.models import models
 from app.models.agent import Agent
 from app.models.role_permission import Permission, Role, RolePermission
@@ -212,6 +213,86 @@ def update_user(
     return _user_response(user)
 
 
+_BUILTIN_USERNAMES = {"acc-mgr", DELETED_USER_USERNAME}
+
+
+def _reassign_user_references(db: Session, old_id: int, new_id: int) -> None:
+    """Reassign all foreign key references from old_id to new_id, then delete
+    records that would be meaningless under deleted-user (api_keys, notifications,
+    project memberships)."""
+    from app.models.apikey import APIKey
+    from app.models.notification import Notification
+    from app.models.activity import Activity
+    from app.models.worklog import WorkLog as WorkLogModel
+    from app.models.meeting import Meeting, MeetingParticipant
+    from app.models.task import Task
+    from app.models.support import Support
+    from app.models.proposal import Proposal
+    from app.models.milestone import Milestone
+    from app.models.calendar import TimeSlot, SchedulePlan
+    from app.models.minimum_workload import MinimumWorkload
+    from app.models.essential import Essential
+
+    # Delete records that are meaningless without the real user
+    db.query(APIKey).filter(APIKey.user_id == old_id).delete()
+    db.query(Notification).filter(Notification.user_id == old_id).delete()
+    db.query(models.ProjectMember).filter(models.ProjectMember.user_id == old_id).delete()
+
+    # Reassign ownership/authorship references
+    db.query(models.Project).filter(models.Project.owner_id == old_id).update(
+        {"owner_id": new_id})
+    db.query(models.Comment).filter(models.Comment.author_id == old_id).update(
+        {"author_id": new_id})
+    db.query(Activity).filter(Activity.user_id == old_id).update(
+        {"user_id": new_id})
+    db.query(WorkLogModel).filter(WorkLogModel.user_id == old_id).update(
+        {"user_id": new_id})
+
+    # Tasks
+    db.query(Task).filter(Task.reporter_id == old_id).update(
+        {"reporter_id": new_id})
+    db.query(Task).filter(Task.assignee_id == old_id).update(
+        {"assignee_id": new_id})
+    db.query(Task).filter(Task.created_by_id == old_id).update(
+        {"created_by_id": new_id})
+
+    # Meetings
+    db.query(Meeting).filter(Meeting.reporter_id == old_id).update(
+        {"reporter_id": new_id})
+    db.query(MeetingParticipant).filter(MeetingParticipant.user_id == old_id).update(
+        {"user_id": new_id})
+
+    # Support
+    db.query(Support).filter(Support.reporter_id == old_id).update(
+        {"reporter_id": new_id})
+    db.query(Support).filter(Support.assignee_id == old_id).update(
+        {"assignee_id": new_id})
+
+    # Proposals
+    db.query(Proposal).filter(Proposal.created_by_id == old_id).update(
+        {"created_by_id": new_id})
+
+    # Milestones
+    db.query(Milestone).filter(Milestone.created_by_id == old_id).update(
+        {"created_by_id": new_id})
+
+    # Calendar
+    db.query(TimeSlot).filter(TimeSlot.user_id == old_id).update(
+        {"user_id": new_id})
+    db.query(SchedulePlan).filter(SchedulePlan.user_id == old_id).update(
+        {"user_id": new_id})
+
+    # Minimum workload / Essential
+    db.query(MinimumWorkload).filter(MinimumWorkload.user_id == old_id).update(
+        {"user_id": new_id})
+    db.query(Essential).filter(Essential.user_id == old_id).update(
+        {"user_id": new_id})
+
+    # Agent profile
+    db.query(Agent).filter(Agent.user_id == old_id).update(
+        {"user_id": new_id})
+
+
 @router.delete("/{identifier}", status_code=status.HTTP_204_NO_CONTENT)
 def delete_user(
     identifier: str,
@@ -223,17 +304,26 @@ def delete_user(
         raise HTTPException(status_code=404, detail="User not found")
     if current_user.id == user.id:
         raise HTTPException(status_code=400, detail="You cannot delete your own account")
-    # Protect built-in accounts from deletion
     if user.is_admin:
         raise HTTPException(status_code=400, detail="Admin accounts cannot be deleted")
-    if user.username == "acc-mgr":
-        raise HTTPException(status_code=400, detail="The acc-mgr account is a built-in account and cannot be deleted")
-    try:
-        db.delete(user)
-        db.commit()
-    except IntegrityError:
-        db.rollback()
-        raise HTTPException(status_code=400, detail="User has related records. Deactivate the account instead.")
+    if user.username in _BUILTIN_USERNAMES:
+        raise HTTPException(
+            status_code=400,
+            detail=f"The {user.username} account is a built-in account and cannot be deleted",
+        )
+
+    deleted_user = db.query(models.User).filter(
+        models.User.username == DELETED_USER_USERNAME
+    ).first()
+    if not deleted_user:
+        raise HTTPException(
+            status_code=500,
+            detail="Built-in deleted-user account not found. Run init_wizard first.",
+        )
+
+    _reassign_user_references(db, user.id, deleted_user.id)
+    db.delete(user)
+    db.commit()
     return None
 
 

app/init_wizard.py

@@ -295,6 +295,39 @@ def init_acc_mgr_user(db: Session) -> models.User | None:
     return user
 
 
+DELETED_USER_USERNAME = "deleted-user"
+
+
+def init_deleted_user(db: Session) -> models.User | None:
+    """Create the built-in deleted-user if not exists.
+
+    This user serves as a foreign key sink: when a real user is deleted,
+    all references are reassigned here instead of cascading deletes.
+    It has no role (no permissions) and cannot log in.
+    """
+    existing = db.query(models.User).filter(
+        models.User.username == DELETED_USER_USERNAME
+    ).first()
+    if existing:
+        logger.info("deleted-user already exists (id=%d), skipping", existing.id)
+        return existing
+
+    user = models.User(
+        username=DELETED_USER_USERNAME,
+        email="deleted-user@harborforge.internal",
+        full_name="Deleted User",
+        hashed_password=None,
+        is_admin=False,
+        is_active=False,
+        role_id=None,
+    )
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+    logger.info("Created deleted-user (id=%d)", user.id)
+    return user
+
+
 def run_init(db: Session) -> None:
     """Main initialization entry point. Reads config from shared volume."""
     config = load_config()
@@ -319,6 +352,9 @@ def run_init(db: Session) -> None:
     # Built-in acc-mgr user (after roles are created)
     init_acc_mgr_user(db)
 
+    # Built-in deleted-user (foreign key sink for deleted accounts)
+    init_deleted_user(db)
+
     # Default project
     project_cfg = config.get("default_project")
     if project_cfg and admin_user: