(feat) Add entropy-based filtering and rolling statistics for k-mers

- Introduce lazy_static dependency
- Refactor encoding: rename encode_base →encode_nuc and make it pub(crate)
- Add from_raw_right/raw Right methods to Kmer for right-aligned handling
- Improve error message formatting and code readability in kmod.rs tests  
- Replace inline entropy computation with precomputed tables (entropy_table module)—using LazyLock for static lookup arrays
- Simplify EntropyFilter by removing redundant tables and delegating to new entropy_table API  
- Add RollingStat module for real-time kmer statistics and minimizer tracking
- Reorganize modules: move iter, encoding to pub(crate), add entropy_table and rolling_stat
- Update imports across obiskbuilder crate accordingly

src/Cargo.lock

@@ -497,6 +497,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+
 [[package]]
 name = "libc"
 version = "0.2.185"
@@ -624,6 +630,7 @@ dependencies = [
 name = "obiskbuilder"
 version = "0.1.0"
 dependencies = [
+ "lazy_static",
  "obikrope",
  "obikseq",
 ]