Fix version commit SHA showing as unknown in Docker (v1.0.1)

The runtime image doesn't include .git, so git rev-parse failed at
startup. Fix: pass COMMIT_SHA as a Docker build arg from github.sha
in CI and bake it into the image as an ENV var, which config.js
already prefers over running git.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "1.0.0",
+  "version": "1.0.1",
   "type": "module",
   "scripts": {
     "dev": "vite",