Fix: Rotate measurement text in SVG export

Previously, measurement text in SVG exports was always horizontal, regardless of the measurement line's orientation.

This change modifies the SvgDrawController.drawText method to:
- Utilize the `textDirection` vector (already calculated by MeasurementEntity) to determine the correct rotation angle for the text.
- Apply an SVG `transform="rotate(...)"` attribute to the <text> element.
- Ensure `text-anchor="middle"` is set when `textAlign` is `center`, to maintain proper centering after rotation.

This addresses issue #37 on GitHub, ensuring that measurement text is correctly aligned and centered with its corresponding line in SVG outputs.

Author: google-labs-jules[bot]

src/drawControllers/svg.drawController.ts

@@ -219,9 +219,21 @@ export class SvgDrawController implements DrawController {
     // No need to handle black to white, as SVG background is white.
     // Other colors will remain as they are.
 
+    let transformAttribute = '';
+    if (textOptions.textDirection) {
+      const angleRadians = Math.atan2(textOptions.textDirection.y, textOptions.textDirection.x);
+      const angleDegrees = angleRadians * 180 / Math.PI;
+      transformAttribute = `transform="rotate(${angleDegrees}, ${canvasBasePoint.x}, ${canvasBasePoint.y})"`;
+    }
+
+    let textAnchorAttribute = '';
+    if (textOptions.textAlign === 'center') {
+      textAnchorAttribute = 'text-anchor="middle"';
+    }
+
 		this.svgStrings.push(
         // Use finalTextColor here
-        `<text x="${canvasBasePoint.x}" y="${canvasBasePoint.y}" fill="${finalTextColor}" font-size="${textOptions.fontSize}" font-family="${textOptions.fontFamily}">${label}</text>`
+        `<text x="${canvasBasePoint.x}" y="${canvasBasePoint.y}" fill="${finalTextColor}" font-size="${textOptions.fontSize}" font-family="${textOptions.fontFamily}" ${transformAttribute} ${textAnchorAttribute}>${label}</text>`
 		);
 	}