feat: add configurable left black safety margin for YouTube cropping …

[djeada]

…in make_short.sh

[Copilot]

Pull Request Overview

This PR adds a configurable left black safety margin feature to the YouTube video cropping functionality in make_short.sh. The feature allows users to specify a left black margin that will be overlaid on the final 1080x1920 output to prevent content from being cut off at the left edge.

• Adds --safe-left command line parameter with default value of 30 pixels
• Implements validation and normalization of the margin value with proper bounds checking
• Overlays a black rectangle on the left side of the final output using FFmpeg's drawbox filter

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