chore(clippy): enable and fix many stricter lints (#3783)

* chore(clippy): enable and fix many stricter lints

These ensure that the codebase uses more idiomatic, performant, and
concise language constructions.

* chore: make non-Clippy compiler warnings also deny by default

apps/app/src/api/utils.rs

@@ -37,6 +37,7 @@ pub fn get_os() -> OS {
     let os = OS::MacOS;
     os
 }
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[allow(clippy::enum_variant_names)]
 pub enum OS {