docs: add v1.2.5 release notes

[dengwx2026]

Summary

• Add v1.2.5 release notes documenting monitoring/metrics enhancements and Aliyun MSE Nacos support
• Update release notes index with v1.2.5 entry
• Update README.md news section and latest updates to reflect v1.2.5

fixes #533

Test plan

• Verify release notes render correctly in Docusaurus
• Verify README.md news table displays properly

🤖 Generated with Claude Code

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⚠️ PR Must Reference an Issue

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1. Adding one of the following keywords in your PR description followed by the issue number:

   • fixes mount path to ro #123
   • closes mount path to ro #123
   • resolves mount path to ro #123
   • refs mount path to ro #123
   • references mount path to ro #123

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   • [FEATURE] Add new feature mount path to ro #123
   • [BUG] Fix critical bug mount path to ro #123

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