feat: Add basic project structure and initial crates

- Added basic project structure with workspace and crates:
  `kvstore`, `vault`, `evm_client`, `cli_app`, `web_app`.
- Created initial `Cargo.toml` files for each crate.
- Added placeholder implementations for key components.
- Included initial documentation files (`README.md`, architecture
  docs, repo structure).
- Included initial implementaion for kvstore crate(async API, backend abstraction, separation of concerns, WASM/native support, testability)
- Included native and browser tests for the kvstore crate

kvstore/src/wasm.rs

@@ -0,0 +1,140 @@
+//! WASM backend for kvstore using IndexedDB (idb crate)
+//!
+//! # Platform
+//!
+//! This backend is only available when compiling for `wasm32` (browser/WebAssembly).
+//! It uses the `idb` crate for async IndexedDB operations.
+//!
+//! # Usage
+//!
+//! This implementation is designed to run inside a browser environment and is not supported on native targets.
+//!
+//! # Example
+//!
+
+
+use crate::traits::KVStore;
+use crate::error::{KVError, Result};
+
+use async_trait::async_trait;
+
+
+#[cfg(target_arch = "wasm32")]
+use idb::{Database, TransactionMode, Factory};
+#[cfg(target_arch = "wasm32")]
+use wasm_bindgen::JsValue;
+#[cfg(target_arch = "wasm32")]
+use js_sys::Uint8Array;
+
+#[cfg(target_arch = "wasm32")]
+const STORE_NAME: &str = "kv";
+
+#[cfg(target_arch = "wasm32")]
+pub struct WasmStore {
+    db: Database,
+}
+
+#[cfg(target_arch = "wasm32")]
+impl WasmStore {
+    pub async fn open(name: &str) -> Result<Self> {
+        let factory = Factory::new().map_err(|e| KVError::Other(format!("IndexedDB factory error: {e:?}")))?;
+        let mut open_req = factory.open(name, None)
+            .map_err(|e| KVError::Other(format!("IndexedDB factory open error: {e:?}")))?;
+        open_req.on_upgrade_needed(|event| {
+            let db = event.database().expect("Failed to get database in upgrade event");
+            if !db.store_names().iter().any(|n| n == STORE_NAME) {
+                db.create_object_store(STORE_NAME, Default::default()).unwrap();
+            }
+        });
+        let db = open_req.await.map_err(|e| KVError::Other(format!("IndexedDB open error: {e:?}")))?;
+        Ok(Self { db })
+    }
+}
+
+#[cfg(target_arch = "wasm32")]
+#[async_trait(?Send)]
+impl KVStore for WasmStore {
+    async fn get(&self, key: &str) -> Result<Option<Vec<u8>>> {
+        let tx = self.db.transaction(&[STORE_NAME], TransactionMode::ReadOnly)
+            .map_err(|e| KVError::Other(format!("idb transaction error: {e:?}")))?;
+        let store = tx.object_store(STORE_NAME)
+            .map_err(|e| KVError::Other(format!("idb object_store error: {e:?}")))?;
+        use idb::Query;
+        let val = store.get(Query::from(JsValue::from_str(key))).await
+            .map_err(|e| KVError::Other(format!("idb get await error: {e:?}")))?;
+        if let Some(jsval) = val {
+            let arr = Uint8Array::new(&jsval);
+            Ok(Some(arr.to_vec()))
+        } else {
+            Ok(None)
+        }
+    }
+    async fn set(&self, key: &str, value: &[u8]) -> Result<()> {
+        let tx = self.db.transaction(&[STORE_NAME], TransactionMode::ReadWrite)
+            .map_err(|e| KVError::Other(format!("idb transaction error: {e:?}")))?;
+        let store = tx.object_store(STORE_NAME)
+            .map_err(|e| KVError::Other(format!("idb object_store error: {e:?}")))?;
+        store.put(&Uint8Array::from(value).into(), Some(&JsValue::from_str(key))).await
+            .map_err(|e| KVError::Other(format!("idb put await error: {e:?}")))?;
+        Ok(())
+    }
+    async fn remove(&self, key: &str) -> Result<()> {
+        let tx = self.db.transaction(&[STORE_NAME], TransactionMode::ReadWrite)
+            .map_err(|e| KVError::Other(format!("idb transaction error: {e:?}")))?;
+        let store = tx.object_store(STORE_NAME)
+            .map_err(|e| KVError::Other(format!("idb object_store error: {e:?}")))?;
+        use idb::Query;
+        store.delete(Query::from(JsValue::from_str(key))).await
+            .map_err(|e| KVError::Other(format!("idb delete await error: {e:?}")))?;
+        Ok(())
+    }
+    async fn contains_key(&self, key: &str) -> Result<bool> {
+        Ok(self.get(key).await?.is_some())
+    }
+
+    async fn keys(&self) -> Result<Vec<String>> {
+        let tx = self.db.transaction(&[STORE_NAME], TransactionMode::ReadOnly)
+            .map_err(|e| KVError::Other(format!("idb transaction error: {e:?}")))?;
+        let store = tx.object_store(STORE_NAME)
+            .map_err(|e| KVError::Other(format!("idb object_store error: {e:?}")))?;
+        let js_keys = store.get_all_keys(None, None).await
+            .map_err(|e| KVError::Other(format!("idb get_all_keys error: {e:?}")))?;
+        let arr = js_sys::Array::from(&JsValue::from(js_keys));
+        let mut keys = Vec::new();
+        for i in 0..arr.length() {
+            if let Some(s) = arr.get(i).as_string() {
+                keys.push(s);
+            }
+        }
+        Ok(keys)
+    }
+
+    async fn clear(&self) -> Result<()> {
+        let tx = self.db.transaction(&[STORE_NAME], TransactionMode::ReadWrite)
+            .map_err(|e| KVError::Other(format!("idb transaction error: {e:?}")))?;
+        let store = tx.object_store(STORE_NAME)
+            .map_err(|e| KVError::Other(format!("idb object_store error: {e:?}")))?;
+        store.clear().await
+            .map_err(|e| KVError::Other(format!("idb clear error: {e:?}")))?;
+        Ok(())
+    }
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+pub struct WasmStore;
+#[cfg(not(target_arch = "wasm32"))]
+#[async_trait]
+impl KVStore for WasmStore {
+    async fn get(&self, _key: &str) -> Result<Option<Vec<u8>>> {
+        Err(KVError::Other("WasmStore is only available on wasm32 targets".to_string()))
+    }
+    async fn set(&self, _key: &str, _value: &[u8]) -> Result<()> {
+        Err(KVError::Other("WasmStore is only available on wasm32 targets".to_string()))
+    }
+    async fn delete(&self, _key: &str) -> Result<()> {
+        Err(KVError::Other("WasmStore is only available on wasm32 targets".to_string()))
+    }
+    async fn exists(&self, _key: &str) -> Result<bool> {
+        Err(KVError::Other("WasmStore is only available on wasm32 targets".to_string()))
+    }
+}