[codex] Update publish expiry defaults

[anarkh]

Summary

• change publish expiry presets to 1周 / 1月 / 长期 / 自定义
• default the publish form to 长期 and keep long-term display as 长期有效
• support custom exact deadlines without a 30-day maximum while keeping the 30-minute lower bound
• update local store and posts cloud function validation for the new expiry model

Impact

• new tasks now stay active by default unless the publisher selects 1周, 1月, or 自定义
• expiry-dependent behavior still uses expiresAt, so comments, trust actions, status display, and share guidance only switch to expired when the chosen deadline passes
• cloud deployment is required before the CloudBase path accepts the new rules

Verification

• node --no-warnings scripts/check-publish-flow.mjs
• npm run check
• bash harness/init.sh
• git diff --check

Manual WeChat DevTools UI verification is still pending because the local 9420 service port remains blocked.