Exercise local device sign-in across restart and storage backends

Assistant-model: GPT-6 Sol
Assistant-workflow: local-device-auth (run cc80c691-7450-4025-bf56-613bc047c5b7)
Assistant-duration: 74m blocked, estimated 60m
Assistant-verification: Bun unit passed: mise exec -- bun test (1563 pass, 2 PostgreSQL skips, 0 fail; one prior unrelated timer flake reproduced as timing-sensitive and passed focused)
Assistant-verification: Postgres startup passed: TEST_DATABASE_URL=chopin_local_auth mise exec -- bun test apps/server/src/storage/postgres/startup.test.ts (1 pass)
Assistant-verification: Playwright E2E passed: flock /tmp/chopin-e2e.lock mise exec -- bun run e2e --workers=1 (231/231, fake GitHub and Bun.secrets boundary)
Assistant-verification: Bun typecheck passed: mise exec -- bun run types (all workspaces and E2E)
Assistant-verification: Bun lint passed: mise exec -- bun run ci (dprint, oxlint, token checks)
Assistant-verification: Bun.secrets native passed: Linux libsecret dummy credential saved, restored and deleted without plaintext copy; only key name and length printed
Assistant-verification: plaintext integration passed: DBUS_SESSION_BUS_ADDRESS=unix:path=/nonexistent process wrote/restored/deleted dummy credential with 0700 directory and 0600 file after secure save failed
Assistant-verification: agent-browser Edge manual unavailable: GitHub sudo password prompt blocked new pddkit approval; no credential restoration claimed
Co-authored-by: Alex Lavaee <lavaman131@github.com>