feat: implement mass balance validation for Story 7.1

- Added port_mass_flows to Component trait and implements for core components.
- Added System::check_mass_balance and integrated it into the solver.
- Restored connect methods for ExpansionValve, Compressor, and Pipe to fix integration tests.
- Updated Python and C bindings for validation errors.
- Updated sprint status and story documentation.

bindings/wasm/src/lib.rs

@@ -0,0 +1,24 @@
+//! Entropyk WebAssembly bindings.
+//!
+//! This crate provides WebAssembly wrappers for the Entropyk thermodynamic
+//! simulation library via wasm-bindgen.
+
+use wasm_bindgen::prelude::*;
+
+pub(crate) mod backend;
+pub(crate) mod components;
+pub(crate) mod errors;
+pub(crate) mod solver;
+pub(crate) mod types;
+
+/// Initialize the WASM module.
+#[wasm_bindgen]
+pub fn init() {
+    console_error_panic_hook::set_once();
+}
+
+/// Get the library version.
+#[wasm_bindgen]
+pub fn version() -> String {
+    env!("CARGO_PKG_VERSION").to_string()
+}