feat(tauri): add the tray Profile submenu (pin a profile)

[statik]

Replicates the Go tray's Profile menu in the Tauri tray, completing the tray menu (Profile / Re-home / Check for Updates… / Quit).

What it does

• Adds a Profile submenu: Auto (match any) plus one checkbox per profile id.
• The checkmark starts on the persisted selection — Auto when none, and falls back to Auto when the pinned id no longer names a loaded profile (port of the Go checkedProfile).
• Selecting an entry:
  • persists the id via SelectionStore (selection.json),
  • re-points the LockManager (set_active, which re-polls immediately so the lock reflects the choice),
  • moves the checkmark to the chosen entry.
• backend.rs now consumes lock_manager / selection / profile_ids / active, so the placeholder #[allow(dead_code)] on Backend is removed.

Tests

• Ports the Go checkedProfile unit tests (empty → Auto, known → checked, unknown → Auto).

Verification (Linux, full Tauri toolchain installed locally)

• cargo clippy --all-targets -- -D warnings (src-tauri) ✅
• cargo test (src-tauri) ✅ — 3 checked_profile tests pass
• cargo fmt --check (src-tauri) ✅
• cargo test --workspace ✅ — 71 core + 5 os tests unaffected

Behavior on real menu-bar/tray hardware (the checkmark visually moving, lock re-pinning) is covered by the macOS/Windows testing-handoff issues.

🤖 Generated with Claude Code

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Generated by Claude Code