feat(desktop): port v0.11.4-v0.15.2 from Tauri to Electron + Discord-parity audio (v0.16.0)

Chronological port of every Tauri release commit (v0.11.4 -> v0.15.2)
into the Electron rebuild, plus Discord-style audio handling that goes
beyond the Tauri original.

Highlights:
  - All 17 Tauri release commits ported (audio fixes, custom notification
    sound, Discord-style chat UX, profile banner, changelog page,
    Discord-parity call UX, screen-share echo + re-watch UX, audio-loop
    fix).
  - Native napi-rs audio-loopback addon with WASAPI process-loopback:
      * EXCLUDE_TARGET_PROCESS_TREE for full-screen shares -> peers
        never hear themselves echoed back through the capture.
      * INCLUDE_TARGET_PROCESS_TREE for window shares -> only the
        picked window's audio is captured, not the whole OS mixer
        (Discord parity).
      * HWND -> PID resolution via Win32 GetWindowThreadProcessId.
  - Discord-style screen-source picker (thumbnail grid, screens vs
    apps tabs, live-refreshing thumbnails).
  - Hash routing fix for packaged builds (file:// can't resolve
    BrowserRouter paths).
  - Tauri sources removed (apps/desktop/src-tauri).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/lib/conversationFeatures.ts

@@ -0,0 +1,129 @@
+import {
+  parseMessagePayload,
+  serializeMessagePayload,
+  type AttachmentHandle,
+  type DecryptedMessage,
+  type PollOption,
+} from '@chat-app/shared/chat';
+
+export type AttachmentBucket = 'media' | 'audio' | 'files';
+
+export interface ConversationAttachmentItem {
+  messageId: string;
+  senderId: string;
+  createdAt: string;
+  handle: AttachmentHandle;
+  bucket: AttachmentBucket;
+}
+
+export interface ConversationAttachmentIndex {
+  all: ConversationAttachmentItem[];
+  media: ConversationAttachmentItem[];
+  audio: ConversationAttachmentItem[];
+  files: ConversationAttachmentItem[];
+}
+
+interface ReactionSummaryInput {
+  emoji: string;
+  count: number;
+  mine: boolean;
+}
+
+export interface PollVoteOptionSummary extends PollOption {
+  count: number;
+  mine: boolean;
+  percent: number;
+}
+
+export interface PollVoteSummary {
+  totalVotes: number;
+  options: PollVoteOptionSummary[];
+}
+
+export const POLL_OPTION_EMOJIS = ['1️⃣', '2️⃣', '3️⃣', '4️⃣', '5️⃣', '6️⃣', '7️⃣', '8️⃣', '9️⃣', '🔟'];
+
+export function collectConversationAttachments(
+  messages: DecryptedMessage[],
+): ConversationAttachmentIndex {
+  const all: ConversationAttachmentItem[] = [];
+
+  for (const message of messages) {
+    if (message.deletedAt || !message.plaintext) continue;
+    const parsed = parseMessagePayload(message.plaintext);
+    if (parsed.kind !== 'text') continue;
+
+    for (const handle of parsed.attachments) {
+      all.push({
+        messageId: message.id,
+        senderId: message.senderId,
+        createdAt: message.createdAt,
+        handle,
+        bucket: bucketForMime(handle.mimeType),
+      });
+    }
+  }
+
+  all.sort((a, b) => Date.parse(b.createdAt) - Date.parse(a.createdAt));
+
+  return {
+    all,
+    media: all.filter((item) => item.bucket === 'media'),
+    audio: all.filter((item) => item.bucket === 'audio'),
+    files: all.filter((item) => item.bucket === 'files'),
+  };
+}
+
+export function createPollPayload(question: string, optionTexts: string[]): string {
+  const trimmedQuestion = question.trim();
+  if (!trimmedQuestion) throw new Error('poll question is required');
+
+  const options: PollOption[] = optionTexts
+    .map((text) => text.trim())
+    .filter(Boolean)
+    .slice(0, POLL_OPTION_EMOJIS.length)
+    .map((text, idx) => ({
+      id: 'option-' + (idx + 1),
+      emoji: POLL_OPTION_EMOJIS[idx]!,
+      text,
+    }));
+
+  if (options.length < 2) throw new Error('poll requires at least two options');
+
+  return serializeMessagePayload({
+    v: 1,
+    type: 'poll',
+    question: trimmedQuestion,
+    options,
+  });
+}
+
+export function summarizePollVotes(
+  options: PollOption[],
+  reactions: ReactionSummaryInput[],
+): PollVoteSummary {
+  const reactionByEmoji = new Map(reactions.map((reaction) => [reaction.emoji, reaction]));
+  const totalVotes = options.reduce(
+    (sum, option) => sum + (reactionByEmoji.get(option.emoji)?.count ?? 0),
+    0,
+  );
+
+  return {
+    totalVotes,
+    options: options.map((option) => {
+      const reaction = reactionByEmoji.get(option.emoji);
+      const count = reaction?.count ?? 0;
+      return {
+        ...option,
+        count,
+        mine: reaction?.mine ?? false,
+        percent: totalVotes > 0 ? Math.round((count / totalVotes) * 100) : 0,
+      };
+    }),
+  };
+}
+
+function bucketForMime(mimeType: string): AttachmentBucket {
+  if (mimeType.startsWith('image/') || mimeType.startsWith('video/')) return 'media';
+  if (mimeType.startsWith('audio/')) return 'audio';
+  return 'files';
+}