feat(ipc): typed bindings for library catalog/genre browse commands

First vertical slice of the tauri-specta rollout: annotate two psysonic-library
browse-metadata commands (library_get_catalog_year_bounds,
library_get_genre_album_counts) with #[specta::specta] and derive specta::Type on
their DTOs (CatalogYearBoundsDto, GenreAlbumCountDto), then add them to
collect_commands!. bindings.ts now carries their typed signatures + DTO shapes
(serde camelCase carried through). Non-breaking: generate_handler! stays the live
handler and nothing imports the bindings yet.

Both DTOs are i64-free (i32/u32/String), so no BigInt handling is needed here —
that convention is decided when the first i64 DTO is annotated. Generated
src/generated is excluded from eslint (its runtime helper uses `any`); tsc still
type-checks bindings.ts.

src-tauri/Cargo.lock

@@ -4261,6 +4261,7 @@ dependencies = [
  "rusqlite",
  "serde",
  "serde_json",
+ "specta",
  "tauri",
  "tokio",
  "wiremock",