feat(bindings): expose RollingVWAP in Python, Node and WASM (R4)

The rolling-window VWAP indicator (`wickra_core::RollingVwap`) was only
available in the Rust crate, even though the README's Volume-family
table already advertised "VWAP (cumulative + rolling)" as a cross-
language feature. Users on Python, Node or in the browser had to fall
back to the cumulative `VWAP` or re-implement the rolling variant
themselves.

This commit closes the gap end-to-end:

- Python: `wickra.RollingVWAP(period)` — same constructor / `update` /
  `batch` / `reset` / `is_ready` / `warmup_period` surface as `VWAP`,
  plus a `period` property and a typed `__repr__`. The `__init__.py`
  re-exports it and `__all__` lists it; the `.pyi` stub matches.
- Node: `RollingVWAP(period)` — napi class with the same lifecycle,
  exported from `index.js` and declared in `index.d.ts`.
- WASM: `RollingVWAP(period)` — wasm-bindgen class with the same
  `Float64Array` I/O as `VWAP`.

Tests added:

- Python: `test_rolling_vwap_streaming_matches_batch` — exercises
  `update == batch` plus the full lifecycle on the shared OHLC fixture.
- Node: `RollingVWAP` row in the `candleScalar` parity table — covered
  by the generic streaming-vs-batch + lifecycle harness.
- WASM: dedicated `wasm-bindgen-test` mirrors the Python test.

The wiki page `Indicator-Vwap.md` drops the "Rust-only" caveat and
gains Python / Node / WASM examples.

bindings/node/src/lib.rs

@@ -899,6 +899,69 @@ impl VwapNode {
     }
 }
 
+#[napi(js_name = "RollingVWAP")]
+pub struct RollingVwapNode {
+    inner: wc::RollingVwap,
+}
+#[napi]
+impl RollingVwapNode {
+    #[napi(constructor)]
+    pub fn new(period: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::RollingVwap::new(period as usize).map_err(map_err)?,
+        })
+    }
+    #[napi(getter)]
+    pub fn period(&self) -> u32 {
+        self.inner.period() as u32
+    }
+    #[napi]
+    pub fn reset(&mut self) {
+        self.inner.reset();
+    }
+    #[napi(js_name = "isReady")]
+    pub fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    #[napi(js_name = "warmupPeriod")]
+    pub fn warmup_period(&self) -> u32 {
+        self.inner.warmup_period() as u32
+    }
+    #[napi]
+    pub fn update(
+        &mut self,
+        high: f64,
+        low: f64,
+        close: f64,
+        volume: f64,
+    ) -> napi::Result<Option<f64>> {
+        Ok(self.inner.update(cnd(high, low, close, volume)?))
+    }
+    #[napi]
+    pub fn batch(
+        &mut self,
+        high: Vec<f64>,
+        low: Vec<f64>,
+        close: Vec<f64>,
+        volume: Vec<f64>,
+    ) -> napi::Result<Vec<f64>> {
+        if high.len() != low.len() || low.len() != close.len() || close.len() != volume.len() {
+            return Err(NapiError::from_reason(
+                "high, low, close, volume must be equal length".to_string(),
+            ));
+        }
+        let mut out = Vec::with_capacity(high.len());
+        for i in 0..high.len() {
+            out.push(
+                self.inner
+                    .update(cnd(high[i], low[i], close[i], volume[i])?)
+                    .unwrap_or(f64::NAN),
+            );
+        }
+        Ok(out)
+    }
+}
+
 #[napi(js_name = "AwesomeOscillator")]
 pub struct AoNode {
     inner: wc::AwesomeOscillator,