Pre-launch checklist for what gets forgotten

Build a pre-launch checklist. ***Not whether features work — what is easy to forget.***

Areas:
1. **Secrets** — keys, tokens, passwords left in the code or the repository, **with how to check**
2. **Authorization** — anything reachable without login that should not be
3. Input validation — when a user enters something strange
4. Error handling — what the user sees on failure; **whether internal errors are exposed**
5. Data — backups, whether deletion is recoverable
6. **Cost** — conditions under which external API or server bills come in unexpectedly
7. If personal data is handled, what is collected and what is disclosed

Output a table: item / how to check / applicable / action.

Rules:
- ***Anything you cannot verify from what I gave you is marked "verify yourself"***, with how.
- ***Do not drop items that do not apply — leave them as "not applicable".*** **Skipped and not-applicable have to be distinguishable.**
- Sort by severity.