[codex] Draft Google Play descriptions

[jjoonleo]

Summary

• Adds draft English and Korean Google Play short and full descriptions for OnTime.
• Documents the shipped-feature basis and product/design review checklist.
• Links the release checklist to the listing-copy source doc.

Closes #447.
References parent track #466.

Verification

• Character-limit check: English short 65/full 1039, Korean short 30/full 471. All are within Google Play limits.
• Forbidden-term scan for ranking/superlative claims: no matches.

Unblocks

• No sub-issue is directly unblocked by code. This gives product/design the copy artifact needed before Play Console listing work continues alongside [Release] Prepare Play listing graphics and launcher icon consistency check #448 and [Release] Capture release screenshots from real app screens #449.