[FIX] charts: bubble legend hover colors

[dhrp-odoo]

Description:

Bubble charts with multiple colors store per-bubble colors as arrays. The legend hover callbacks reused line chart highlighting, which expects single color values and crashes when resetting highlights.

Use bubble-specific highlighting based on the original hover colors so legend hover works with per-bubble colors and preserves transparency.

Task: 6269018

review checklist

• feature is organized in plugin, or UI components
• support of duplicate sheet (deep copy)
• in model/core: ranges are Range object, and can be adapted (adaptRanges)
• in model/UI: ranges are strings (to show the user)
• undo-able commands (uses this.history.update)
• multiuser-able commands (has inverse commands and transformations where needed)
• new/updated/removed commands are documented
• exportable in excel
• translations (_t("qmsdf %s", abc))
• unit tested
• clean commented code
• track breaking changes
• doc is rebuild (npm run doc)
• status is correct in Odoo

[robodoo]