feat: introduce --color-icons palette for icon colors

[yasyuk]

Summary

• Adds 10 new --color-icons-* CSS variables (yellow, orange, red, pink, purple, blue, ice, teal, lime, grey) to _vars.scss — same values for both light and dark modes
• Updates all iconColor-* SCSS classes in icon.scss to reference the new palette instead of the generic --color-* variables
• Updates iconObject.scss so the isTask.isDone checkmark uses --color-icons-lime
• Updates theme.ts icon bg and color sections (light + dark) to use the new palette values

Test plan

• Verify icon colors (grey, yellow, orange, red, pink, purple, blue, ice, teal, lime) match the new palette in light mode
• Verify same colors appear unchanged in dark mode
• Check task objects: undone task icon uses tertiary color, done task icon uses --color-icons-lime
• Check object type icons in sidebar, dataview, and search results show updated colors

🤖 Generated with Claude Code

[github-actions]

CLA Assistant Lite bot:
Thank you for your pull request, we really appreciate it!

Please sign our Contributor License Agreement before we can accept your contribution.
You can sign the CLA by simply commenting on this pull request with the following text.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request}

[Toseef-Ahmad]

@yasyuk Hi add this line as it is in the description:
I understand that contributing to this repository will require me to agree with the CLA