docs: add version management section to README

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -120,6 +120,52 @@ After pulling, update `core_version` in `VERSIONS.json`.
 
 ---
 
+## Version Management
+
+### Releasing a New Version
+
+```bash
+# 1. Update VERSIONS.json (project_version, last_updated, notes)
+# 2. Commit
+git add VERSIONS.json
+git commit -m "chore: bump version to vX.Y.Z"
+
+# 3. Tag (MUST be after VERSIONS.json update)
+git tag -a vX.Y.Z -m "vX.Y.Z: release description"
+
+# 4. Push commit + tag
+git push origin main
+git push origin vX.Y.Z
+
+# 5. Update Gitea description (Settings page or API)
+```
+
+Version must match in all three places: `VERSIONS.json`, git tag, and Gitea description.
+
+### Download / Switch to an Older Version
+
+```bash
+# List all versions
+git tag -l
+
+# Switch to a specific version
+git checkout v1.1.0
+
+# Compare versions
+git diff v1.1.0 v1.2.0
+
+# Download as zip (no clone needed)
+curl -o zpark-ems-v1.1.0.zip \
+  "http://100.69.143.96:3300/tianpu/zpark-ems/archive/v1.1.0.zip"
+
+# Go back to latest
+git checkout main
+```
+
+See [ems-core README](http://100.69.143.96:3300/tianpu/ems-core) for the full version management guide.
+
+---
+
 ## License
 
 Copyright 2026. All rights reserved.