Allow FSRS simulator to target the current deck

Problem

The FSRS simulator currently initializes its card scope from the current preset, and the simulator UI does not expose that search. When a preset is shared by multiple decks, users cannot easily simulate workload for only the deck they are currently configuring.

This is a focused subset of the broader simulator-improvement discussion in #5609.

Proposed behavior

Expose the simulator's existing search field and provide quick choices for:

• current preset
• current deck only
• current deck + subdecks

The default should remain the current preset-wide search, and suspended cards should continue to be excluded by default.

The backend already supports this through SimulateFsrsReviewRequest.search, so this should be a UI-only change with no scheduler or database changes.

Motivation

Deck-scoped simulation is useful when multiple subjects/decks share one preset but the user wants to estimate workload for one deck without changing preset assignments.

A proof-of-concept add-on has already been built and tested against Anki's native simulator backend.