Fix/animation offload to cpu

[ahrefabhi]

Problem

When hovering over points on time-series charts rendered with uPlot, the library changes border-color based on series color. This animation occurs during the composition state where border-color cannot be GPU-accelerated, causing the browser to offload the rendering work to the CPU. This results in:

• Main thread blocking during hover interactions
• Janky animations and degraded user experience
• Potential frame drops, especially on lower-end devices.

📸 Screenshots / Screen Recording (if applicable / mandatory for UI related changes)

Before:

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After:

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Closes https://github.com/SigNoz/engineering-pod/issues/3625

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Note

Reduces animation overhead by eliminating broad transitions and scoping effects to cheaper properties.

• Removes global * transition rules and the .no-transition utility from styles.scss
• Narrows .u-marker transitions from all 0.2s to transform 0.2s in enhanced legend styles (right and bottom variants)
• Keeps prefers-reduced-motion handling intact

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