v2: Persistent sessions — named storage profiles

[loyality7]

Context

Cookies and storage are process-global in v1, cleared between sessions. Some callers want a logged-in session to survive an app restart — a "profile" concept, explicitly managed rather than pretending to be OS-level isolation.

Scope

• Named profiles: cookies, localStorage, sessionStorage saved and restored by name.
• Explicit clearing per profile and per domain.
• Documentation keeps stating plainly that this is managed isolation, not platform isolation — cookies remain process-global underneath.

Acceptance criteria

• A named profile's cookies/storage survive an app process restart
• Clearing one profile does not affect another
• Docs/KDoc explicitly restate the process-global caveat on every profile-related API
• Device test: save profile, kill process, restore profile, confirm logged-in state persists