update toolchain and rust edition

Dependencies

• [2] 6YZAVBWU Initial commit
• [3] KLR5FRIB add fs state read/write of repos
• [4] SWWE2R6M display basic repo stuff
• [5] KT5UYXGK fix selection after adding file, add changed file diffs
• [6] YBJRDOTC make all repo actions async
• [7] IQDCHWCP load a pijul repo
• [8] 3GZPRZXC s/-/_ in crate paths
• [9] ELG3UDT6 allow to rm added files

Change contents

• replacement in rust-toolchain.toml at line 2
  [3.2173]→[3.2173:2192](∅→∅)
  − channel = "1.83.0"
  [3.2173]
  + channel = "1.85.1"
• replacement in justfile at line 11
  [2.181]→[3.2238:2270](∅→∅)
  − nightly := "nightly-2024-11-14"
  [2.181]

  [2.181]
  + nightly := "nightly-2025-04-24"
• replacement in crates/libflowers_client/src/repo.rs at line 210
  [6.3220]→[4.962:1017](∅→∅),[4.962]→[4.962:1017](∅→∅)
  − repo.path.iter().last().unwrap().to_string_lossy()
  [6.3220]

  [4.1017]
  + repo.path.iter().next_back().unwrap().to_string_lossy()
• replacement in crates/libflowers_client/src/repo.rs at line 433
  [5.1590]→[6.3810:3870](∅→∅)
  − panic!("Failed to track file with: {}", e);
  [5.1590]

  [5.1640]
  + panic!("Failed to track file with: {e}");
• replacement in crates/flowers_ui/src/main.rs at line 43
  [6.5062]→[6.5062:5139](∅→∅)
  − panic!("invalid `{}` environment variable {}", LOG_ENV, err)
  [6.5062]

  [6.5139]
  + panic!("invalid `{LOG_ENV}` environment variable {err}")
• replacement in Cargo.toml at line 11
  [2.3917]→[2.3917:3934](∅→∅)
  − edition = "2021"
  [2.3917]

  [2.3934]
  + edition = "2024"