Fix Link wallet disconnect recovery

[fmhall]

Link disconnect requires a recent sign-in. Older valid sessions received a generic connection error, and the sign-in page redirected authenticated users home, preventing recovery.

This adds a phone reauthentication flow that returns to the wallet page, separates disconnect failures from connection failures, and shows recovery messages based on the current wallet state. The existing ownership, session freshness, and revoke-before-delete checks remain in place.

Validation:

• pnpm check — lint, types, formatting, Knip, and 788 tests.
• pnpm build — production build with local placeholder database and Kernel values.
• Regression coverage exercises stale-session rejection, a newly issued phone session, failed revocation retaining the account, successful disconnect, and stale errors after account removal.

The integration uses the real Better Auth Link plugin and PGlite with mocked provider HTTP. Live Link revocation and phone OTP delivery were not exercised.