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/utils/registerDesktopMediaSaver.ts

@@ -0,0 +1,111 @@
+import { registerMediaSaver } from './saveMedia';
+import { isElectron, isTauri } from './tauri';
+
+type ElectronSaveResult = {
+  success?: boolean;
+  canceled?: boolean;
+  path?: string;
+  error?: string;
+};
+
+type ElectronMediaApi = {
+  saveFile?: (payload: {
+    filename: string;
+    mimeType?: string;
+    data: Uint8Array;
+  }) => Promise<ElectronSaveResult>;
+};
+
+async function blobToUint8Array(blob: Blob): Promise<Uint8Array> {
+  const buffer = await blob.arrayBuffer();
+  return new Uint8Array(buffer);
+}
+
+function guessFilters(filename: string, mimeType?: string): Array<{ name: string; extensions: string[] }> {
+  const ext = filename.includes('.') ? filename.split('.').pop()!.toLowerCase() : '';
+  const mime = (mimeType || '').toLowerCase();
+
+  if (mime.startsWith('image/') || ['png', 'jpg', 'jpeg', 'gif', 'webp', 'bmp', 'svg'].includes(ext)) {
+    return [
+      { name: 'Images', extensions: ['png', 'jpg', 'jpeg', 'gif', 'webp', 'bmp', 'svg'] },
+      { name: 'All Files', extensions: ['*'] },
+    ];
+  }
+  if (mime.startsWith('video/') || ['mp4', 'webm', 'mkv', 'mov'].includes(ext)) {
+    return [
+      { name: 'Videos', extensions: ['mp4', 'webm', 'mkv', 'mov'] },
+      { name: 'All Files', extensions: ['*'] },
+    ];
+  }
+  if (mime.startsWith('audio/') || ['mp3', 'ogg', 'wav', 'm4a', 'flac'].includes(ext)) {
+    return [
+      { name: 'Audio', extensions: ['mp3', 'ogg', 'wav', 'm4a', 'flac'] },
+      { name: 'All Files', extensions: ['*'] },
+    ];
+  }
+  if (mime === 'application/pdf' || ext === 'pdf') {
+    return [
+      { name: 'PDF', extensions: ['pdf'] },
+      { name: 'All Files', extensions: ['*'] },
+    ];
+  }
+  if (ext) {
+    return [
+      { name: ext.toUpperCase(), extensions: [ext] },
+      { name: 'All Files', extensions: ['*'] },
+    ];
+  }
+  return [{ name: 'All Files', extensions: ['*'] }];
+}
+
+async function saveWithElectron(blob: Blob, filename: string): Promise<void> {
+  const media = (window.electron as { media?: ElectronMediaApi } | undefined)?.media;
+  if (!media?.saveFile) {
+    throw new Error('Electron media.saveFile is unavailable');
+  }
+
+  const data = await blobToUint8Array(blob);
+  const result = await media.saveFile({
+    filename,
+    mimeType: blob.type || 'application/octet-stream',
+    data,
+  });
+
+  if (result?.canceled) return;
+  if (result?.success === false) {
+    throw new Error(result.error || 'Failed to save file');
+  }
+}
+
+async function saveWithTauri(blob: Blob, filename: string): Promise<void> {
+  const { save } = await import('@tauri-apps/plugin-dialog');
+  const { writeFile } = await import('@tauri-apps/plugin-fs');
+
+  const path = await save({
+    defaultPath: filename,
+    filters: guessFilters(filename, blob.type),
+  });
+  if (!path) return;
+
+  const data = await blobToUint8Array(blob);
+  await writeFile(path, data);
+}
+
+/**
+ * Wire Electron / Tauri native save dialogs into core saveMedia helpers.
+ * Call once at desktop app startup. No-ops in plain browser.
+ */
+export function registerDesktopMediaSaver(): void {
+  if (isElectron()) {
+    registerMediaSaver(async (blob, filename) => {
+      await saveWithElectron(blob, filename);
+    });
+    return;
+  }
+
+  if (isTauri()) {
+    registerMediaSaver(async (blob, filename) => {
+      await saveWithTauri(blob, filename);
+    });
+  }
+}