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/native/audio-loopback/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "audio-loopback"
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+publish = false
+description = "Native Windows process-loopback audio capture for ChatApp Electron"
+
+[lib]
+crate-type = ["cdylib"]
+
+# Reduce binary size on release builds and avoid the default-features
+# panic-handler that bloats node addons. We don't strip — keeping symbols
+# helps debug crashes from a packaged build.
+[profile.release]
+lto = true
+codegen-units = 1
+panic = "abort"
+
+[dependencies]
+napi = { version = "2", default-features = false, features = ["napi6"] }
+napi-derive = "2"
+
+[target.'cfg(target_os = "windows")'.dependencies]
+# Match the Tauri reference exactly. Cargo.lock there pins 0.15.0; the
+# 0.15 family exposes AudioClient::new_application_loopback_client(pid,
+# include_tree) which is the load-bearing API for EXCLUDE_TARGET_PROCESS_TREE.
+wasapi = "0.15"
+
+[build-dependencies]
+napi-build = "2"