Add Discord-native hybrid front-end for Jarvis (bot + bridge)

Transform isair/jarvis into a Discord-controlled voice assistant running on
the Ubuntu VNC desktop, keeping the mature ~39k-line Python brain intact.

- bot/ (Node + bun, discord.js): /자비스 slash commands (ephemeral),
  voice channel join + voice receive/playback, pluggable VNC screen broadcast
  (selfbot live / noVNC / screenshot)
- bridge/ (Python, Flask): wraps jarvis STT + run_reply_engine + Piper TTS
  behind a thin localhost HTTP API
- .env.example, scripts/ (start_bridge/start_bot/dev), README rewrite,
  docs/language-comparison.md and docs/vnc-xfce-setup.md

Language decision: hybrid (Python brain + Node/bun Discord layer) because
Discord blocks bot video; native screen broadcast only works via a Node
selfbot library.

scripts/build_installer.sh

@@ -0,0 +1,51 @@
+#!/bin/bash
+# Build the frozen app for manual testing. On macOS this produces
+# dist/Jarvis.app; on Linux dist/Jarvis/. There is no Inno-equivalent
+# installer step on these platforms, so the bundle directory itself is
+# the artefact you'd ship.
+
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+PROJECT_ROOT="$(pwd)"
+
+# Stamp a dev version file so jarvis.get_version() works in the bundle.
+GIT_SHA="$(git rev-parse --short=7 HEAD 2>/dev/null || echo local)"
+DEV_VERSION="dev-${GIT_SHA}"
+echo "[build_installer] Stamping dev _version.py (${DEV_VERSION})..."
+cat > "${PROJECT_ROOT}/src/jarvis/_version.py" <<EOF
+# Auto-generated by scripts/build_installer.sh
+VERSION = "${DEV_VERSION}"
+RELEASE_CHANNEL = "develop"
+EOF
+
+echo "[build_installer] 🎨 Generating icons..."
+python src/desktop_app/desktop_assets/generate_icons.py
+
+echo "[build_installer] 🧹 Cleaning previous builds..."
+rm -rf build dist
+
+echo "[build_installer] 📦 Running PyInstaller..."
+python -m PyInstaller jarvis_desktop.spec
+
+if [[ "$OSTYPE" == "darwin"* ]]; then
+    if [[ -d dist/Jarvis.app ]]; then
+        echo
+        echo "[build_installer] ✅ SUCCESS"
+        echo "                  Bundle: ${PROJECT_ROOT}/dist/Jarvis.app"
+        echo "[build_installer] ℹ️  No installer is produced on macOS."
+    else
+        echo "[build_installer] ❌ Bundle missing at dist/Jarvis.app" >&2
+        exit 1
+    fi
+else
+    if [[ -d dist/Jarvis ]]; then
+        echo
+        echo "[build_installer] ✅ SUCCESS"
+        echo "                  Bundle: ${PROJECT_ROOT}/dist/Jarvis"
+        echo "[build_installer] ℹ️  No installer is produced on Linux."
+    else
+        echo "[build_installer] ❌ Bundle missing at dist/Jarvis" >&2
+        exit 1
+    fi
+fi