feat: user-choosable avatar colors with settings picker

Add avatarColor as a stored, user-selectable field (mint, sky, lavender,
coral, rose, teal, amber). Randomly assigned on registration, changeable
in profile settings. Existing users keep hash-based fallback until they
choose a color. Includes DB migration, API validation, gradient map,
live preview in settings, and banner fallback integration.

packages/web/src/components/chat/FriendsPage.test.tsx

@@ -50,6 +50,7 @@ const makeFriend = (overrides: Partial<TaggedFriend> = {}): TaggedFriend => ({
   avatar: null,
   banner: null,
   accentColor: null,
+  avatarColor: null,
   bio: null,
   status: 'online',
   customStatus: null,
@@ -75,6 +76,7 @@ const makeRequest = (overrides: Partial<TaggedFriendRequest> = {}): TaggedFriend
     avatar: null,
     banner: null,
     accentColor: null,
+    avatarColor: null,
     bio: null,
     status: 'online',
     customStatus: null,
@@ -235,6 +237,7 @@ describe('FriendsPage', () => {
           avatar: null,
           banner: null,
           accentColor: null,
+          avatarColor: null,
           bio: null,
           status: 'online',
           customStatus: null,
@@ -286,6 +289,7 @@ describe('FriendsPage', () => {
           avatar: null,
           banner: null,
           accentColor: null,
+          avatarColor: null,
           bio: null,
           status: 'online',
           customStatus: null,
@@ -332,6 +336,7 @@ describe('FriendsPage', () => {
           avatar: null,
           banner: null,
           accentColor: null,
+          avatarColor: null,
           bio: null,
           status: 'online',
           customStatus: null,