Fix mobile Mega Menu UX — independent column toggles, optional titles, improved hamburger

[CySSoO]

Motivation

• Fix mobile mega menu so the hamburger is visually clear and does not overlap header icons.
• Ensure opening one mobile section never closes others and each menu level is independent.
• Make column titles optional and avoid rendering empty markup to prevent visual shift.

Description

• Update views/templates/hook/prettyblocks/prettyblock_megamenu_item.tpl to separate the navigation link from the mobile toggle, add a dedicated mobile toggle button, and render per-column collapsible blocks with unique IDs so each column manages its own open/closed state (no shared accordion or data-bs-parent).
• Change views/templates/hook/prettyblocks/prettyblock_megamenu_container.tpl to use a dedicated toggler class and markup (everblock-megamenu-toggler / everblock-megamenu-toggler-icon) for a clearer hamburger control.
• Add CSS in views/css/everblock.css to restyle the hamburger, toggle icons, and mobile collapse behavior so the menu opens full-width/full-height (fixed), keeps the toggle visible, and animates mobile chevrons; also ensure the mobile container background and spacing are correct.
• Preserve constraints: no PrestaShop core changes and no external JS added; the solution relies on per-item Bootstrap collapse attributes and template changes only.

Testing

• No automated tests were executed on these changes.

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Codex Task