Use GIT_COMMIT_SHA env var instead of execSync for Docker compatibility

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

next.config.ts

@@ -1,16 +1,5 @@
-import { execSync } from "node:child_process";
 import type { NextConfig } from "next";
 
-process.env.GIT_COMMIT_SHA = (() => {
-  try {
-    return execSync("git rev-parse --short HEAD", {
-      encoding: "utf-8",
-    }).trim();
-  } catch {
-    return "unknown";
-  }
-})();
-
 const imageBaseUrl = process.env.TMDB_IMAGE_BASE_URL || "";
 const imageHost = imageBaseUrl
   ? new URL(imageBaseUrl).hostname