R1:f95913ec47c9

Phriction basics

Summary:
Basically a copy/paste of parts of D636, but with two changes:

- Fully separate the index table ("document") from the content table
("content"). I think this will be a cleaner solution in the long run.
- Build slugs into the document structure.

This doesn't do anything useful, it just normalizes slugs and lays some
groundwork.

Test Plan:
- Visited various /w/ pages and saw them normalize correctly.
- Verified the DAO works by inserting dummy rows.

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