Enable Ruff rule PLC0415: import-outside-top-level

### Feature Request

### Problem / Opportunity

Per [this comment](https://github.com/internetarchive/openlibrary/pull/11071#discussion_r2229601568) we want to enable this rule.

First step: Try to turn on PLC0415 and deal with ~200 cases where it complains.

### Proposal

### Breakdown

### Related files

Refer to [this map of common Endpoints](https://github.com/internetarchive/openlibrary/wiki/Endpoints):
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### Requirements Checklist
Checklist of requirements that need to be satisfied in order for this issue to be closed:
* [ ]

### Stakeholders

*

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