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/README.md

@@ -0,0 +1,52 @@
+# kvstore: Async Key-Value Store for Native and WASM
+
+`kvstore` provides a runtime-agnostic, async trait for key-value storage, with robust implementations for both native (using `sled`) and browser/WASM (using IndexedDB via the `idb` crate) environments.
+
+## Features
+- **Unified async trait**: Same API for all platforms. Methods: `get`, `set`, `remove`, `contains_key`, `keys`, `clear`.
+- **Native backend**: Uses `sled` for fast, embedded storage. Blocking I/O is offloaded with `tokio::task::spawn_blocking`.
+- **WASM backend**: Uses IndexedDB via the `idb` crate for browser storage. Fully async and Promise-based.
+- **Error handling**: Consistent error types across platforms.
+- **Conditional compilation**: Uses Cargo features and `cfg` to select the backend.
+
+## Usage
+
+Add to your `Cargo.toml`:
+```toml
+[dependencies]
+kvstore = { path = "../kvstore" }
+```
+
+### Example
+```rust
+use kvstore::{KVStore, NativeStore};
+
+#[tokio::main]
+async fn main() {
+    let store = NativeStore::open("/tmp/mydb").unwrap();
+    store.set("foo", b"bar").await.unwrap();
+    let val = store.get("foo").await.unwrap();
+    println!("Got: {:?}", val);
+}
+```
+
+For WASM/browser, use `WasmStore` and run in a browser environment.
+
+## Testing
+
+### Native
+```sh
+cargo test -p kvstore --features native
+```
+
+### WASM (browser)
+```sh
+cd kvstore
+wasm-pack test --headless --firefox --features web
+```
+
+## Architecture
+- See `../docs/Architecture.md` for full design details.
+
+## License
+MIT OR Apache-2.0