Design optional local profiles as a future account foundation

[ZFordDev]

Goal

Allow multiple people or planning contexts to use separate local SchedPlus profiles while keeping the application fully usable without an online account. A local profile is not authentication and must not be presented as security.

Design requirements

• Existing installations become a default local profile without losing or relocating data unexpectedly.
• Each profile has isolated tasks and preferences, with explicit backup, restore, import, and export behavior.
• Profile switching is clear and does not leave reminder or undo state attached to the wrong profile.
• Stable local profile identifiers can later be linked to an optional online identity.
• Deleting a profile requires explicit confirmation and a recoverable safety backup.
• The architecture does not make login, network access, or cloud storage mandatory.

Acceptance criteria

• Threat model and non-security nature of local profiles are documented.
• Database and filesystem isolation strategy is approved.
• Migration and rollback behavior for existing users is tested.
• Profile creation, rename, switch, export, and deletion workflows are defined.
• Future account linkage can be added without changing ordinary task IDs or forcing existing users online.