✨ vanth/store, tests: Add persistent SQLite and in-memory store backends with CRUD operations

- Added `rusqlite` and `sqlx` dependencies to support SQLite backend functionality for the store.
- Implemented `Store` struct with backend switching between in-memory (`HashMap`) and SQLite-based storage.
- Added CRUD operations (`read`, `write`, `delete`) to the `Store` API with error handling.
- Created integration tests for SQLite store persistence and basic operations.

crates/vanth/tests/integration/store.rs

@@ -0,0 +1,26 @@
+use vanth::store::Store;
+use std::path::PathBuf;
+use tempfile::TempDir;
+
+#[test]
+fn test_sqlite_store() {
+    let dir = TempDir::new().unwrap();
+    let path = dir.path().join("test.db");
+    let mut store = Store::from_path(path.clone()).unwrap();
+    
+    assert_eq!(store.read(b"key_1"), Ok(None));
+    assert_eq!(store.write(b"key_1", b"value_1"), Ok(()));
+    
+    let value = store.read(b"key_1").unwrap();
+    assert_eq!(value.as_deref(), Some(b"value_1" as &[u8]));
+    
+    drop(store);
+    
+    let mut store = Store::from_path(path.clone()).unwrap();
+    
+    let value = store.read(b"key_1").unwrap();
+    assert_eq!(value.as_deref(), Some(b"value_1" as &[u8]));
+    
+    store.delete(b"key_1").unwrap();
+    assert_eq!(store.read(b"key_1"), Ok(None));
+}