remove echarts, use canvas

src/lib/charts/bands.ts

@@ -0,0 +1,24 @@
+/**
+ * Daylight Bands
+ *
+ * Converts sunrise/sunset timestamp arrays into neutral background band
+ * descriptors that CanvasChart renders as shaded daylight areas.
+ */
+
+/** A background band on the time axis, expressed in epoch seconds. */
+export interface DaylightBand {
+	/** Band start (epoch seconds) */
+	start: number;
+	/** Band end (epoch seconds) */
+	end: number;
+}
+
+/**
+ * Builds daylight bands from sunrise/sunset arrays.
+ *
+ * @param sunrise - Array of sunrise timestamps (unix seconds)
+ * @param sunset  - Array of sunset timestamps (unix seconds)
+ */
+export function buildDaylightBands(sunrise: number[], sunset: number[]): DaylightBand[] {
+	return sunrise.map((r, i) => ({ start: r, end: sunset[i] }));
+}