Add grep search functionality - Issue #86 (#87)

* Add grep search functionality to LeannSearcher

- Add use_grep parameter to search method
- Implement grep-based search on .jsonl files
- Add fallback Python regex search
- Support same SearchResult format as semantic search

Addresses issue #86

* fix: resolve linting errors

* docs: add grep search example

* docs: add grep search to README examples

* refactor: remove regex fallback, move grep example to features section

* docs: add grep search to Advanced Features with comprehensive guide

uv.lock

@@ -1564,7 +1564,7 @@ name = "importlib-metadata"
 version = "8.7.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
-    { name = "zipp" },
+    { name = "zipp", marker = "python_full_version < '3.10'" },
 ]
 sdist = { url = "https://files.pythonhosted.org/packages/76/66/650a33bd90f786193e4de4b3ad86ea60b53c89b669a5c7be931fac31cdb0/importlib_metadata-8.7.0.tar.gz", hash = "sha256:d13b81ad223b890aa16c5471f2ac3056cf76c5f10f82d6f9292f0b415f389000", size = 56641, upload-time = "2025-04-27T15:29:01.736Z" }
 wheels = [
@@ -2117,7 +2117,7 @@ wheels = [
 
 [[package]]
 name = "leann-backend-diskann"
-version = "0.3.2"
+version = "0.3.3"
 source = { editable = "packages/leann-backend-diskann" }
 dependencies = [
     { name = "leann-core" },
@@ -2129,14 +2129,14 @@ dependencies = [
 
 [package.metadata]
 requires-dist = [
-    { name = "leann-core", specifier = "==0.3.2" },
+    { name = "leann-core", specifier = "==0.3.3" },
     { name = "numpy" },
     { name = "protobuf", specifier = ">=3.19.0" },
 ]
 
 [[package]]
 name = "leann-backend-hnsw"
-version = "0.3.2"
+version = "0.3.3"
 source = { editable = "packages/leann-backend-hnsw" }
 dependencies = [
     { name = "leann-core" },
@@ -2149,7 +2149,7 @@ dependencies = [
 
 [package.metadata]
 requires-dist = [
-    { name = "leann-core", specifier = "==0.3.2" },
+    { name = "leann-core", specifier = "==0.3.3" },
     { name = "msgpack", specifier = ">=1.0.0" },
     { name = "numpy" },
     { name = "pyzmq", specifier = ">=23.0.0" },
@@ -2157,7 +2157,7 @@ requires-dist = [
 
 [[package]]
 name = "leann-core"
-version = "0.3.2"
+version = "0.3.3"
 source = { editable = "packages/leann-core" }
 dependencies = [
     { name = "accelerate" },