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.

bot/src/stream/novnc.ts

@@ -0,0 +1,34 @@
+/**
+ * noVNC link backend (safe, real-time, no ban risk).
+ *
+ * Does not broadcast natively into Discord. Instead it shares a noVNC web URL
+ * that anyone can open in a browser to watch (and optionally control) the VNC
+ * desktop live. Set NOVNC_URL in .env (e.g. http://192.168.10.9:6080/vnc.html).
+ *
+ * Stand up noVNC once on the host with websockify, e.g.:
+ *   websockify --web=/usr/share/novnc 6080 localhost:5901
+ */
+import type { AppConfig } from "../config.ts";
+import type { ScreenStreamer, StreamContext } from "./index.ts";
+
+export class NoVncStreamer implements ScreenStreamer {
+  readonly kind = "novnc" as const;
+  private active = false;
+  constructor(private config: AppConfig) {}
+
+  isActive() {
+    return this.active;
+  }
+
+  async start(_ctx: StreamContext): Promise<string> {
+    if (!this.config.novncUrl) {
+      return "NOVNC_URL이 설정되지 않았습니다 (.env). 예: http://192.168.10.9:6080/vnc.html";
+    }
+    this.active = true;
+    return `🖥️ VNC 화면 실시간 보기 (브라우저): ${this.config.novncUrl}`;
+  }
+
+  async stop(): Promise<void> {
+    this.active = false;
+  }
+}