dave: include anonymous user identifier in api call

- don't include users pubkey

This could be used to associate requests with real users,
rendering the anonymized user_id pointless

TODO: Implement a new tool call that lets dave ask for your pubkey

Fixes: #834
Fixes: #836
Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_dave/Cargo.toml

@@ -6,6 +6,7 @@ version.workspace = true
 [dependencies]
 async-openai = "0.28.0"
 egui = { workspace = true }
+sha2 = { workspace = true }
 notedeck = { workspace = true }
 notedeck_ui = { workspace = true }
 eframe = { workspace = true }