Document SQLite design decisions

[mcm001]

Description

Document what I remember about how SQLite came to be and some surrounding context. Would love help digging up the old links, CD threads, Discord reports, etc mentioned in the diff.

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2024.3.1
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added

[Gold856]

Here's a Discord report: https://discord.com/channels/725836368059826228/725836368680583201/1159220410940919859