Atproto, types overhaul and error handling

Breaks off from Atrium-rs's types because they are implemented
inconsistently, which makes them harder to use.

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~

atproto/Cargo.toml

@@ -8,5 +8,7 @@ atrium-api = { version = "0.25.3", default-features = false }
 lazy-regex = "3.4.1"
 serde.workspace = true
 serde_json.workspace = true
+time = { version = "0.3.41", features = ["parsing", "formatting"] }
 tracing-subscriber.workspace = true
 tracing.workspace = true
+thiserror.workspace = true