feat: Refactor kvstore and vault to use features and logging

- Remove hardcoded dependencies in kvstore Cargo.toml; use features
  instead. This allows for more flexible compilation for different
  targets (native vs. WASM).
- Improve logging in vault crate using the `log` crate. This makes
  debugging easier and provides more informative output during
  execution.  Native tests use `env_logger`, WASM tests use
  `console_log`.
- Update README to reflect new logging best practices.
- Add cfg attributes to native and wasm modules to improve clarity.
- Update traits.rs to specify Send + Sync behavior expectations.

kvstore/src/wasm.rs

@@ -13,12 +13,15 @@
 //!
 
 
+//! WASM backend for kvstore using IndexedDB (idb crate)
+//! Only compiled for wasm32 targets
+
+#[cfg(target_arch = "wasm32")]
 use crate::traits::KVStore;
+#[cfg(target_arch = "wasm32")]
 use crate::error::{KVError, Result};
-
+#[cfg(target_arch = "wasm32")]
 use async_trait::async_trait;
-
-
 #[cfg(target_arch = "wasm32")]
 use idb::{Database, TransactionMode, Factory};
 #[cfg(target_arch = "wasm32")]