chore: move env examples to env-example/ and unify CDN env source

- Reorganize env example files into a dedicated env-example/ directory for clarity
- Update .gitignore to ignore env files (with examples now in env-example/)
- Unify CDN credentials (CF_ZONE_ID / CF_API_TOKEN) to be sourced from .env.local in both test and production deploys
- Update git_hooks/post-receive to copy production env example from new location
- Update deploy scripts (pre_release_web.sh, release_web.sh) to copy the appropriate env example into .env.local before building
- Update _deploy_lib.sh purge_cdn_cache to source from .env.local instead of .env

.gitignore

@@ -30,16 +30,11 @@ yarn-debug.log*
 yarn-error.log*
 .pnpm-debug.log*
 
-# env files (can opt-in for committing if needed)
+# env files 
 .env
 .env.local
 .env.development
-.env.test
 .env.production
-!.env.example
-!.env.development.example
-!.env.test.example
-!.env.production.example
 
 # deploy archives (scripts/deploy/_deploy_lib.sh 的 archive() 生成)
 archives/