docs: bump to v0.6.0, point historical versions to git.codingplan.site

- badge: v0.5.2 -> v0.6.0, link to GitHub releases
- release history: replace v0.5.1 'latest' with v0.6.0 notes
- history section: link git.codingplan.site for v0.5.x and earlier
- .gitignore: exclude .release* (private release-notes drafts)
- README_EN: same updates in English

.gitignore

@@ -13,3 +13,4 @@ Snipaste_*.png
 
 # 内部设计规范与实施计划，仅供本地查阅，不入版本库
 docs/superpowers/
+.release*