Scaffold Rust API and worker workspace

Pin the Rust toolchain and nextest profile so both service crates share a reproducible verification baseline.

crates/remora-worker/src/lib.rs

@@ -0,0 +1,11 @@
+pub const COMPONENT_NAME: &str = "remora-worker";
+
+#[cfg(test)]
+mod tests {
+    use super::COMPONENT_NAME;
+
+    #[test]
+    fn exposes_component_name() {
+        assert_eq!(COMPONENT_NAME, "remora-worker");
+    }
+}

crates/remora-worker/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("{}", remora_worker::COMPONENT_NAME);
+}