refactor: simplify hash algorithm API and remove custom hasher implementation (#37)

- Remove custom hasher.rs module and Hasher trait
- Replace with HashAlgorithm enum for better type safety
- Simplify hash calculation from write()+sum() to hash_encode()
- Remove stateful hasher operations (reset, write, sum)
- Update all hash usage in ecstore client modules
- Maintain compatibility with existing checksum functionality

crates/utils/src/lib.rs

@@ -30,8 +30,6 @@ pub mod io;
 #[cfg(feature = "hash")]
 pub mod hash;
 
-pub mod hasher;
-
 #[cfg(feature = "os")]
 pub mod os;