feat(whatsapp): auto-provision Docker bridge per tenant

- Add Dockerfile.whatsapp-bridge with Baileys + env var support
- Modify whatsapp-bridge-server.js to accept PORT, TENANT_ID, WEBHOOK_BASE
- Add internal_bp.py with endpoints to provision/destroy bridges via Docker
- Register internal_bp in app.py
- Each tenant gets isolated container, port, and volume

pos/Dockerfile.whatsapp-bridge

@@ -0,0 +1,20 @@
+FROM node:20-alpine
+
+WORKDIR /app
+
+# Install git and build tools (needed for some npm deps)
+RUN apk add --no-cache git python3 make g++
+
+# Install dependencies
+COPY whatsapp-bridge-package.json package.json
+RUN npm install
+
+# Copy bridge server
+COPY whatsapp-bridge-server.js .
+
+# Create auth directory
+RUN mkdir -p /app/auth
+
+EXPOSE 21465
+
+CMD ["node", "whatsapp-bridge-server.js"]