feat: env-var-ize WS URL as CUSTOM_VITE_WS_URL, add .env.example

Dockerfile.canvas

@@ -6,6 +6,9 @@ FROM node:20-alpine AS frontend-builder
 
 WORKDIR /app
 
+ARG CUSTOM_VITE_WS_URL
+ENV CUSTOM_VITE_WS_URL=$CUSTOM_VITE_WS_URL
+
 COPY package*.json ./
 RUN --mount=type=cache,target=/root/.npm npm ci --ignore-scripts
 

docker-compose.yml

@@ -15,6 +15,8 @@ services:
     build:
       context: .
       dockerfile: Dockerfile.canvas
+      args:
+        - CUSTOM_VITE_WS_URL=${CUSTOM_VITE_WS_URL:-wss://excalidraw.forkless.com}
     image: celstnblacc/excalidraw-mcp-sentinel-canvas:latest
     container_name: mcp-excalidraw-canvas
     ports:

frontend/src/App.tsx

@@ -435,7 +435,7 @@ function App(): JSX.Element {
       return
     }
 
-    const wsUrl = 'wss://excalidraw.forkless.com'
+    const wsUrl = import.meta.env.CUSTOM_VITE_WS_URL || 'wss://excalidraw.forkless.com'
     
     websocketRef.current = new WebSocket(wsUrl)
     

vite.config.js

@@ -1,9 +1,14 @@
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 
+const wsUrl = process.env.CUSTOM_VITE_WS_URL || 'wss://excalidraw.forkless.com';
+
 export default defineConfig({
   root: 'frontend',
   plugins: [react()],
+  define: {
+    'import.meta.env.CUSTOM_VITE_WS_URL': JSON.stringify(wsUrl),
+  },
   build: {
     outDir: '../dist/frontend',
     emptyOutDir: true,