Fix OpenCL HoughLines incorrect theta range handling

The OpenCL implementation of cv::HoughLines was ignoring the user-provided
min_theta and max_theta range, always assuming a full [0, PI) span. This leads
to a mismatch between CPU and OCL results for limited-angle Hough transforms.

Changes in this PR

• Pass minTheta, maxTheta, and computed theta_step from the C++ dispatcher
• Update get_lines OpenCL kernel to compute:
  angle = minTheta + idx * theta_step
• Add USE_MINMAX_THETA build flag for clarity and kernel configuration
• Add CPU vs OCL consistency test for restricted-angle HoughLines

Why this matters

This bug caused incorrect results when using min_theta/max_theta on GPU via UMat.
This PR aligns OpenCL behavior with the CPU implementation and restores
correctness for limited-angle Hough transforms.

Issue

Fixes#28036

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