add lsh hashing support

ReadMe.md

@@ -217,6 +217,78 @@ let keys = adaptive_probe(
 );
 ```
 
+## LSH Index
+
+For efficient similarity search using Locality-Sensitive Hashing:
+
+```rust
+use redoal::{Point, normalize, resample, spectral_signature, lsh::LSHIndex};
+
+// Create LSH index with default parameters (4 tables, 8 dimensions, 12 projections)
+let mut index = LSHIndex::new(4, 8, 12);
+
+// Process gesture and extract spectral embedding
+let gesture = vec![
+    Point::new(0.0, 0.0),
+    Point::new(1.0, 0.0),
+    Point::new(0.5, 1.0),
+];
+
+let norm = normalize(&gesture);
+let resamp = resample(&norm, 64);
+let spectral: Vec<f32> = spectral_signature(&resamp, 8)
+    .iter()
+    .map(|x| *x as f32)
+    .collect();
+
+// Insert gesture into index
+index.insert(spectral);
+
+// Query for similar gestures
+let query = vec![
+    Point::new(0.1, 0.1),
+    Point::new(1.1, 0.1),
+    Point::new(0.6, 1.1),
+];
+
+let norm_query = normalize(&query);
+let resamp_query = resample(&norm_query, 64);
+let spectral_query: Vec<f32> = spectral_signature(&resamp_query, 8)
+    .iter()
+    .map(|x| *x as f32)
+    .collect();
+
+let results = index.query_knn(&spectral_query, 3);
+for result in results {
+    println!("Found similar gesture: {:?}", result);
+}
+```
+
+### LSH Features
+
+- **Deterministic Initialization**: Fixed seeds for reproducible results
+- **Multi-table Indexing**: 4 tables by default for improved recall
+- **Projection-based Hashing**: ≤64 projections (u64 bit limit)
+- **L2 Distance Ranking**: Always rank results by distance
+- **Multi-probe Search**: Query neighboring buckets for better results
+- **Vector Normalization**: Built-in normalization support
+
+### LSH Usage Example with Multi-probe
+
+```rust
+let mut index = LSHIndex::new(4, 8, 12);
+
+// Insert gestures
+let gesture1 = vec![1.0, 0.5, 0.3, 0.2, 0.1, 0.05, 0.03, 0.02];
+let gesture2 = vec![1.1, 0.4, 0.35, 0.15, 0.12, 0.04, 0.02, 0.01];
+index.insert(gesture1);
+index.insert(gesture2);
+
+// Query with multi-probe (checks neighboring buckets)
+let query = vec![1.05, 0.45, 0.32, 0.18, 0.11, 0.045, 0.025, 0.015];
+let results = index.query_knn_multi_probe(&query, 3, 2); // k=3, probe 2 bits
+```
+
 ## HNSW Index
 
 For fast local similarity search on peers: