feat: add user color customization and metadata handling

- Implemented `useUserColor` hook to manage user profile color stored in avatar PNG metadata.
- Added `useOtherUserColor` hook to fetch and cache colors from other users' avatars.
- Created utility functions for reading and writing PNG metadata, enabling color embedding and extraction.
- Refactored `SearchResultGroup`, `RoomInput`, `Message`, `RoomPinMenu`, and `Notifications` components to utilize user color for display.
- Introduced `UserColorPicker` component in settings for users to select and save their profile color.
- Enhanced notification and message rendering to prioritize custom user colors over legacy colors.

src/app/features/room/message/Message.tsx

@@ -80,6 +80,7 @@ import { PowerIcon } from '../../../components/power';
 import colorMXID from '../../../../util/colorMXID';
 import { getPowerTagIconSrc } from '../../../hooks/useMemberPowerTag';
 import { Presence, useUserPresence } from '../../../hooks/useUserPresence';
+import { useOtherUserColor } from '../../../hooks/useUserColor';
 
 export type ReactionHandler = (keyOrMxc: string, shortcode: string) => void;
 
@@ -736,6 +737,9 @@ export const Message = as<'div', MessageProps>(
       getMemberDisplayName(room, senderId) ?? getMxIdLocalPart(senderId) ?? senderId;
     const senderAvatarMxc = getMemberAvatarMxc(room, senderId);
 
+    // Get custom user color from avatar metadata (takes priority)
+    const customUserColor = useOtherUserColor(senderId, senderAvatarMxc);
+
     const tagColor = memberPowerTag?.color
       ? accessibleTagColors?.get(memberPowerTag.color)
       : undefined;
@@ -743,7 +747,8 @@ export const Message = as<'div', MessageProps>(
       ? getPowerTagIconSrc(mx, useAuthentication, memberPowerTag.icon)
       : undefined;
 
-    const usernameColor = legacyUsernameColor ? colorMXID(senderId) : tagColor;
+    // Priority: custom user color > tag color (non-legacy) > colorMXID (legacy)
+    const usernameColor = customUserColor ?? (legacyUsernameColor ? colorMXID(senderId) : tagColor);
 
     const headerJSX = !collapse && (
       <Box