fix: give each assignee avatar its own color

[Mario-Mohar]

What

Derives the assignee avatar colour from the assignee's name instead of hardcoding bg-purple-700.

Adds an AVATAR_COLORS palette and a getAvatarColor(name) helper next to the existing getTagColor, in the same style.

Why

Every avatar circle was the same purple, so on a board with several assignees the badges were indistinguishable and the colour carried no information.

One deviation from the suggestion in the issue: the hash sums every character of the name rather than using charCodeAt(0). With only the first character, any two names sharing a first letter — Bea and Ben, Anna and Alex — still collide, which is the common case on a small team and exactly what the issue is about. Summing the whole string costs one extra line and avoids that.

Frontend only, no backend changes. With a fixed palette collisions are still possible for enough distinct names; the goal here is distinguishability, not uniqueness.

Testing

Ran the board locally with six assignees chosen to cover the whole palette — Bea, Ben, Vera, Amir, Anna, Maja — and each avatar rendered a different colour. Bea and Ben share a first letter and still come out purple vs. blue, which is the case the wider hash is for. No console errors.

Closes #109

[Mario-Mohar]

Hi @anoopcodehack — friendly nudge on this one too, in case it got buried.

TaskCard.jsx has changed since I opened this (#473 and #475 both touched it), so I re-checked against current main: the PR still merges cleanly, and the fix is still needed — the assignee avatar is still hardcoded to bg-purple-700, so every avatar renders the same colour.

It adds an AVATAR_COLORS palette and a getAvatarColor(name) helper right next to the existing TAG_COLORS/getTagColor, following the same pattern, and closes #109.

One thing worth your eye, since it deviates from the issue: I sum every character of the name rather than using charCodeAt(0). With only the first character, names sharing a first letter — Bea and Ben, Anna and Alex — still collide, which is the common case on a small team. Happy to switch it to the literal suggestion if you prefer.