fix: make canvas import optional for ARM64 compatibility

src/modules/social-poster/image-renderer.service.ts

@@ -2,7 +2,16 @@ import { Injectable, Logger, OnModuleInit } from "@nestjs/common";
 import * as fs from "fs";
 import * as path from "path";
 import axios from "axios";
-import { createCanvas, loadImage } from "canvas";
+// Canvas is optional – native module may fail on ARM64 (RPi)
+let createCanvas: any;
+let loadImage: any;
+try {
+  const canvas = require("canvas");
+  createCanvas = canvas.createCanvas;
+  loadImage = canvas.loadImage;
+} catch {
+  // Canvas unavailable – ImageRendererService methods will throw at runtime if called
+}
 import { PredictionCardDto } from "./dto/prediction-card.dto";
 
 @Injectable()