Modernize dependencies, add wishlist features, improve error handling

- Remove once_cell and serde dependencies; use std::sync::LazyLock
  and manual serde_json::Value parsing instead
- Add wishlist support: load wishlist from my_cars.json, prefix
  missing cars with '+' in missing mode, add 'wishlist' command
  to show stale wishlist entries (prefixed with '-')
- Replace unwrap()/expect() with graceful eprintln warnings and
  early returns throughout (get_car_list, parse_car_times, etc.)
- Scope all Mutex locks tightly to avoid holding during I/O
  (print_best_times, print_best_cars, print_trash, print_wishlist_stale)
- Replace custom split_prefix_postfix with str::split_once
- Pass owned-car set into parse_all_times/parse_car_times via
  Arc<HashSet> instead of reading file per task
- Consolidate my_cars.json loading into single load_my_cars_data()
  returning both owned and wishlist sets
- Add .gitignore and Cargo.lock to version control
- Report task failures in parse_all_times join loop

Cargo.toml

@@ -17,8 +17,6 @@ reqwest = "0.12.15"
 tokio = { version = "1.44.1", features = ["full"] }
 serde_json = "1.0.140"
 futures = "0.3.31"
-once_cell = "1.20.2"
-serde = { version = "1.0.210", features = ["derive"] }
 
 [dev-dependencies]
 tempfile = "3.10.1"