Add automatic build version generation from git

Implement a script to automatically generate build version information from git commit hash and date, updating version.json and creating latest.json.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 77cfe984-2c65-4152-bb7a-0df28274fe66
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Replit-Commit-Event-Id: ab5429c1-7925-4a30-a964-b3db9c5772da
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scripts/update-version.mjs

@@ -0,0 +1,32 @@
+#!/usr/bin/env node
+import { execSync } from "node:child_process";
+import { readFileSync, writeFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, resolve } from "node:path";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const versionPath = resolve(__dirname, "..", "version.json");
+
+function git(args) {
+  return execSync(`git ${args}`, { encoding: "utf8" }).trim();
+}
+
+let commit = "unknown";
+let date = new Date().toISOString().slice(0, 10).replace(/-/g, "");
+try {
+  commit = git("log -1 --format=%h");
+  date = git("log -1 --format=%cd --date=format:%Y%m%d");
+} catch (err) {
+  console.warn(`[update-version] git unavailable, using fallback: ${err.message}`);
+}
+
+const build = `${date}.${commit}`;
+const current = JSON.parse(readFileSync(versionPath, "utf8"));
+const next = { ...current, build };
+
+if (current.build === build) {
+  console.log(`[update-version] build unchanged: ${build}`);
+} else {
+  writeFileSync(versionPath, JSON.stringify(next, null, 2) + "\n");
+  console.log(`[update-version] ${current.build} -> ${build}`);
+}