Merge pull request #29299 from AyushDas4890:fix/doc-typos-tutorials

Fix typos in tutorial documentation #29299

This PR fixes spelling typos across several tutorial documentation files (dnn, calib3d, objdetect, app, js_tutorials), including `export=dowload` -> `export=download` in the DNN text-spotting tutorial's Google Drive URLs.

Documentation-only change; no functional code is affected.

Pull Request Readiness Checklist:

[x] I agree to contribute to the project under Apache 2 License.

[x] To the best of my knowledge, the proposed patch is not based on code under GPL or another license that is incompatible with OpenCV.

[x] The PR is proposed to the proper branch (4.x).

[x] Documentation-only change; no accuracy/performance tests or opencv_extra patch are applicable.

doc/js_tutorials/js_core/js_basic_ops/js_basic_ops.markdown

@@ -105,7 +105,7 @@ let mat = new cv.Mat();
 let matVec = new cv.MatVector();
 // Push a Mat back into MatVector
 matVec.push_back(mat);
-// Get a Mat fom MatVector
+// Get a Mat from MatVector
 let cnt = matVec.get(0);
 mat.delete(); matVec.delete(); cnt.delete();
 @endcode