fix(parser): support directory paths with spaces in LIST command (#530)

[snowyukitty]

Summary

Fixes #530.

When parsing the FTP LIST command with an argument containing spaces (such as LIST path with spaces), the parser previously performed a .split(|&b| b == b' ') and took .next(), causing the path to be truncated after the first space (resulting in path: Some("path")).

Changes

1. src/server/controlchan/line_parser/parser.rs:
   • Updated LIST parameter parsing to iteratively strip leading hyphen-prefixed option flags (e.g. -la, -x) and support the -- option delimiter.
   • Preserved the entire remaining path string with embedded spaces intact.
2. src/server/controlchan/line_parser/tests.rs:
   • Added unit test cases for LIST covering paths with spaces, multiple option flags, wildcard patterns, leading dashes with --, and whitespace-only input.
3. tests/list.rs:
   • Added an end-to-end integration test creating a directory hierarchy with spaces (test_list_dir_spaces/sub folder/nested_target) and verifying that LIST test_list_dir_spaces/sub folder successfully returns the nested entries over the data channel.
4. Cargo.toml:
   • Fixed workspace relative path for unftp-sbe-fs dev-dependency.

Verification

• Passed all 69 unit tests and 26 doctests (cargo test).
• Passed integration test suite including tests/list.rs.
• Verified clean cargo clippy --all-targets --all-features and cargo fmt --check.