chore: add changelog for version 0.5.13

[EKKOLearnAI]

Summary

• Add changelog entries for v0.5.13 covering all PRs merged since v0.5.12
• Add i18n translations for all 8 locales (en, zh, de, es, fr, ja, ko, pt)

v0.5.13 Changes

1. Message queue for sequential run processing (feat: add message queue for sequential run processing #501)
2. Two-level skills directory with misc category (feat: support two-level skills directory structure with misc category (雜項) #500)
3. Filter ephemeral sessions during startup sync (fix: filter out ephemeral sessions during startup sync #503)
4. Termux/proot environment compatibility (feat: add Termux/proot environment compatibility #457)
5. Chat run abort lifecycle handling ([codex] Handle chat run abort lifecycle #454)
6. Remove streaming indicator from history (fix: remove streaming indicator from history message list #456)
7. Fix context resolution for custom providers (Fix context resolution for custom providers #468)
8. Fix IPv6 listen default (Fix IPv6 listen default #470)
9. Improve chat message display and compression (fix: improve chat message display and compression logic #476)
10. Fix chat sound toggle and cron silent history (修复聊天完成提示音开关不生效 #466, 修复 cron 静默运行时历史为空 #463)

Test plan

• i18n coverage test passes
• Verify changelog modal shows v0.5.13 correctly
• Verify all 8 locales render without missing keys

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