Bump min rust version to 1.91 (wasm-pack v0.15 needs it)

Author: ImplOfAnImpl

Cargo.toml

@@ -127,7 +127,7 @@ utxo = { path = "utxo" }
 
 [workspace.package]
 edition = "2024"
-rust-version = "1.88"
+rust-version = "1.91"
 version = "1.3.0"
 license = "MIT"