Add a project-recovery flow when sync returns PROJECT_NOT_FOUND

[ivklgn]

Problem

When the server no longer recognizes a project (e.g. it was removed), sync fails opaquely instead of guiding the user to recover.

Expected result

Sync detects a PROJECT_NOT_FOUND response and offers to re-create the project and re-sync (respecting non-interactive mode).

Impact

Turns a confusing hard failure into a clear, recoverable flow.

Scope

• Detect the PROJECT_NOT_FOUND response in the sync client.
• Prompt to re-create and re-run sync; respect non-interactive mode.
• Tests with an httptest server returning the error.

Files: cmd/sync.go, internal/api/, internal/sync/ (+ tests)

Acceptance: a missing-project sync offers a clear recovery path.

Status: blocked — requires the server-side PROJECT_NOT_FOUND response and the sync feature to be un-gated.