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.

.env.example

@@ -0,0 +1,67 @@
+# ============================================================================
+# Javis Bot — environment configuration
+# Copy to `.env` and fill in.  Never commit your real `.env`.
+# ============================================================================
+
+# ---------------------------------------------------------------------------
+# Discord bot (normal bot account) — voice I/O + slash commands
+# ---------------------------------------------------------------------------
+# From https://discord.com/developers/applications  → your app
+DISCORD_BOT_TOKEN=
+DISCORD_APP_ID=
+# The (single) server this bot serves. Guild-scoped commands appear instantly.
+DISCORD_GUILD_ID=
+
+# ---------------------------------------------------------------------------
+# Brain bridge (Python service in bridge/) — STT + reply engine + TTS
+# ---------------------------------------------------------------------------
+BRIDGE_URL=http://127.0.0.1:8765
+BRIDGE_HOST=127.0.0.1
+BRIDGE_PORT=8765
+JARVIS_BRAIN_ENABLED=1
+JARVIS_TTS_ENABLED=1
+# faster-whisper device/compute. On this RTX 5050 box: cuda / float16.
+WHISPER_DEVICE=auto
+WHISPER_COMPUTE_TYPE=auto
+# Optional explicit Piper voice model (.onnx). If empty, the jarvis default is used.
+TTS_PIPER_MODEL_PATH=
+
+# ---------------------------------------------------------------------------
+# Jarvis brain (Ollama-backed). See src/jarvis/config.py for the full list.
+# ---------------------------------------------------------------------------
+OLLAMA_BASE_URL=http://127.0.0.1:11434
+# OLLAMA_CHAT_MODEL=...
+# WHISPER_MODEL=...
+
+# ---------------------------------------------------------------------------
+# VNC screen broadcast
+#   selfbot    = real live "Go Live" stream (needs a USER/burner token; ToS risk)
+#   novnc      = share a noVNC browser link (safe, real-time, not native)
+#   screenshot = periodic screenshots to the channel (safe, low fps)
+#   none       = disabled
+# ---------------------------------------------------------------------------
+STREAM_BACKEND=selfbot
+
+# The VNC desktop runs on X display :1 (see docs/vnc-xfce-setup.md)
+VNC_DISPLAY=:1
+VNC_RESOLUTION=1920x1080
+VNC_FRAMERATE=30
+VNC_BITRATE_KBPS=4000
+
+# --- selfbot backend ---
+# A THROWAWAY/burner Discord user account token. NEVER your main account.
+# Using a selfbot violates Discord ToS and can get the account banned.
+DISCORD_SELFBOT_TOKEN=
+
+# --- novnc backend ---
+# e.g. http://192.168.10.9:6080/vnc.html  (websockify --web=/usr/share/novnc 6080 localhost:5901)
+NOVNC_URL=
+
+# --- screenshot backend ---
+SCREENSHOT_INTERVAL_SEC=5
+
+# ---------------------------------------------------------------------------
+# Voice behaviour
+# ---------------------------------------------------------------------------
+# Silence (ms) that marks the end of an utterance before sending to the brain.
+VOICE_SILENCE_MS=800