[FEATURE] Support multiple team owners and ownership continuity #652

Problem

For self-hosted Voltius deployments, team ownership should not remain tied to a single founding user.

A team can have administrators and members, but for long-term operation there should also be a way to have multiple owners at the same time.

This is especially important for company or shared self-hosted installations. The person who originally creates the team or self-hosted workspace may later leave the organization, change responsibilities, or simply no longer need to use Voltius.

The team should not depend permanently on that original account.

Requested behavior

Allow more than one team member to have the Owner role.

An existing owner should be able to:

• promote another eligible member to Owner;
• invite a user directly as an Owner, if appropriate;
• have multiple Owners active at the same time;
• demote an Owner when at least one other Owner remains;
• leave the team without affecting its continued operation, provided another Owner remains.

The system should prevent removing, demoting, or allowing the departure of the last remaining Owner.

For example:

Team
├── Alice   Owner
├── Bob     Owner
├── Carol   Manager
└── Dave    Member

If Alice originally created the team and later leaves:

Team
├── Bob     Owner
├── Carol   Manager
└── Dave    Member

the team should continue normally under Bob's ownership.

Ownership should belong to the team, not permanently to its creator

Ideally, the account that originally creates a team should not retain any permanent hidden or special status once other Owners exist.

After creation, the founding Owner should simply be one of the current Owners.

This would make ownership a property of the team's membership and role model rather than a permanent relationship between the team and its original creator.

Self-hosted use case

This matters particularly for self-hosted deployments.

A company may run its own Voltius server and create a shared team vault for infrastructure administration.

The administrator who initially deploys Voltius may later:

• leave the company;
• move to another role;
• hand responsibility to another administrator;
• stop using their Voltius account.

It should be possible to transfer responsibility without recreating the team, migrating its vaults, or retaining the original administrator's account indefinitely.

Suggested rules

A possible ownership model could be:

• a team must always have at least one Owner;
• a team may have any number of Owners;
• only an Owner may grant or revoke the Owner role;
• an Owner cannot remove or demote the final remaining Owner;
• the final Owner cannot leave the team until another Owner has been assigned;
• existing Manager / Editor / Member / Connect-only permissions can remain unchanged.

For sensitive ownership changes, an explicit confirmation could be shown.

Reference model

Bitwarden/Vaultwarden organizations use a similar model.

An organization may have multiple Owners, and Bitwarden explicitly recommends assigning additional Owners for continuity and failover. Ownership is therefore not permanently tied to the account that originally created the organization.

A similar model would fit Voltius well, especially for self-hosted and company deployments.

Relationship to existing team work

This appears related to the existing team administration/offboarding work, especially:

• Team administration & offboarding — roles, pending-invite status, seats, leave/remove #72 — Team administration & offboarding
• Explicit "Share" verb for vaults — a real share sheet, and unify the two invite panels #68 — Share/team role model

Those issues already use an owner / manager / editor / member / connect-only role vocabulary.

This request is specifically about making Owner a true transferable and multi-member ownership role, so a team can survive the departure of its original creator.