Replace manual CLI parsing with clap derive

- Add clap dependency with derive feature for structured CLI argument parsing
- Replace env::args() manual matching with clap subcommands (fetch, best, missing, wishlist, trash, details, track)
- Change print_best_car() signature from (&String, &String, &String) to (&str, &str, u8) for idiomatic Rust
- Add TODO.md tracking known tech debt and planned features
- Update CHANGELOG.md with clap migration details and set v0.2.0 release date

TODO.md

@@ -0,0 +1,4 @@
+1) **Move shell post-processing into Rust** — `full_script` does `sort`, `grep`, file splitting via shell. Add native subcommands (`very-best`, `add`, `remove`) or CLI flags (`--min-count`, `--sort-by`) so the binary produces the final files directly. Modify the script to export to files, nothing else.
+2) **Correct `+` prefix semantics** — `+` means "not on wishlist". It is not needed in `best`/`missing` output but is used as "add to wishlist". Since we incorporated the wishlist actions into the application, the prefix can go.
+3) **Add `all` subcommand** — `full_script` runs 5 commands sequentially, each parsing all timing files independently. A single `all` command would parse once and write all outputs, cutting runtime ~80%.
+4) **Document the daily workflow** — README and USER_GUIDE don't explain `full_script` or the relationship between Rust output and the files (`sorted.csv`, `very_best.csv`, `wishlist.csv`, `add.csv`).