Improve Prettyblock simple image slider spacing and controls

[CySSoO]

Motivation

• Make the central image larger when the Prettyblock simple image slider is active so the focal slide stands out.
• Add padding/gap around the slider so side images don't appear visually cut off.
• Ensure navigation arrows are visible and provide proper disabled styling so controls are usable and clear.

Description

• Updated views/css/everblock.css to add outer padding on .ever-slider and column-gap plus vertical padding on .ever-slider-track to create spacing around items and avoid cropped edges.
• Increased the active slide scale from scale(1.08) to scale(1.15) on .ever-slider-item.is-active to enlarge the central image.
• Added visible arrow indicators via ::before on .ever-slider-prev/.ever-slider-next, added disabled styling for these buttons, and added responsive padding/gap adjustments for max-width breakpoints in views/css/everblock.css.
• Synchronized the JS calculation in views/js/everblock-slider.js by changing the active-width CSS variable multiplier from 1.08 to 1.15 so button positioning remains correct with the new scale.

Testing

• No automated tests were executed for this change in the repository during this rollout.

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Codex Task