Add MSC4522 username colors, release notes dialog, and profile layout fixes.

Replace legacy profile style metadata with MSC4133 profile fields, add in-app update notes, tighten account profile name spacing, and wire desktop media save helpers through the client.

src/app/state/releaseNotes.ts

@@ -0,0 +1,55 @@
+import { atom } from 'jotai';
+
+const LAST_SEEN_VERSION_KEY = 'paarrot:lastSeenVersion';
+const PENDING_RELEASE_NOTES_KEY = 'paarrot:pendingReleaseNotes';
+
+export type PendingReleaseNotes = {
+  version: string;
+  releaseNotes: unknown;
+};
+
+export type ReleaseNotesDialogState = {
+  open: boolean;
+  /** Opened from About instead of an automatic post-update prompt. */
+  manual: boolean;
+};
+
+export const releaseNotesDialogAtom = atom<ReleaseNotesDialogState>({
+  open: false,
+  manual: false,
+});
+
+export function getLastSeenAppVersion(): string | null {
+  return localStorage.getItem(LAST_SEEN_VERSION_KEY);
+}
+
+export function setLastSeenAppVersion(version: string): void {
+  localStorage.setItem(LAST_SEEN_VERSION_KEY, version);
+}
+
+export function storePendingReleaseNotes(version: string, releaseNotes: unknown): void {
+  try {
+    localStorage.setItem(
+      PENDING_RELEASE_NOTES_KEY,
+      JSON.stringify({ version, releaseNotes } satisfies PendingReleaseNotes)
+    );
+  } catch {
+    // ignore quota errors
+  }
+}
+
+export function getPendingReleaseNotes(): PendingReleaseNotes | null {
+  try {
+    const raw = localStorage.getItem(PENDING_RELEASE_NOTES_KEY);
+    if (!raw) return null;
+    const parsed = JSON.parse(raw) as PendingReleaseNotes;
+    if (typeof parsed?.version !== 'string') return null;
+    return parsed;
+  } catch {
+    return null;
+  }
+}
+
+export function clearPendingReleaseNotes(): void {
+  localStorage.removeItem(PENDING_RELEASE_NOTES_KEY);
+}