refactor: modular architecture with unified error handling and DashMap concurrency

- Break monolithic records.rs into commands/, output/, parsing/ modules
- Add lib.rs with shared types (AppError, Car, BestCarRecord, etc.)
- Replace Arc<Mutex<HashMap>> with DashMap for concurrent access
- Add unified AppError enum with thiserror
- Add configurable CLI paths (--my-cars, --cars-db, --times-dir, --tracks-db)
- Add serde deserialization for Car struct
- Add CSV escaping for fields with commas/quotes/newlines
- Fix track name splitting: split_once -> rsplit_once for _a handling
- Add integration tests, proptest property-based tests, and unit tests
- Add rustfmt.toml configuration
- Update documentation (API, ARCHITECTURE, DATA_STRUCTURES, README)

Cargo.toml

@@ -13,10 +13,14 @@ path = "src/records.rs"
 
 [dependencies]
 reqwest = "0.12.15"
-tokio = { version = "1.44.1", features = ["full"] }
+tokio = { version = "1.44.1", features = ["rt-multi-thread", "macros", "fs", "sync", "io-util"] }
+serde = { version = "1", features = ["derive"] }
 serde_json = "1.0.140"
 futures = "0.3.31"
 clap = { version = "4", features = ["derive"] }
+thiserror = "2"
+dashmap = "6"
 
 [dev-dependencies]
 tempfile = "3.10.1"
+proptest = "1"