fix: integrate AI cross-platform start scripts

Former-commit-id: 2054b6036d

start-backend.js

@@ -0,0 +1,20 @@
+const { execSync } = require("child_process");
+const path = require("path");
+const fs = require("fs");
+
+const backendDir = path.resolve(__dirname, "backend");
+const venvBin = process.platform === "win32"
+  ? path.join(backendDir, "venv", "Scripts", "python.exe")
+  : path.join(backendDir, "venv", "bin", "python3");
+
+if (!fs.existsSync(venvBin)) {
+  console.error(`[!] Python venv not found at: ${venvBin}`);
+  console.error("[!] Run start.sh (Mac/Linux) or start.bat (Windows) first to create the venv.");
+  process.exit(1);
+}
+
+console.log(`[*] Starting backend with: ${venvBin}`);
+execSync(`"${venvBin}" -m uvicorn main:app --reload`, {
+  cwd: backendDir,
+  stdio: "inherit",
+});