Atproto, types overhaul and error handling

Breaks off from Atrium-rs's types because they are implemented
inconsistently, which makes them harder to use. Additionally, I wanted
sqlx support so I decided I'd need to reimplement them to some extent
anyways.

This was done with reference to the atproto documentation but
specifically not the atrium-rs codebase so I wouldn't have to think
about licenses.

This adds the types and error module in atproto. It also touches
Cargo.toml for some new dependencies and some shared dependencies. It
required thiserror, so I looped that into the workspace meaning that
this commit touches db.

some things to keep in mind:
- There is no CID parsing
- None of this is tested, nor are there any tests written. We're playing
  fast and loose baby~

db/Cargo.toml

@@ -4,8 +4,8 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-thiserror = "2.0.12"
 atproto.workspace = true
 async-trait.workspace = true
-sqlx = { version = "0.8.6", features = ["postgres", "runtime-tokio"] }
+sqlx.workspace = true
+thiserror.workspace = true
 tokio.workspace = true