chore(corp/rih): bootstrap backend application with rouille

Change-Id: I48b0c432a843db5a44b3a3de09f18e1232644a44
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8715
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

corp/rih/backend/default.nix

@@ -0,0 +1,16 @@
+{ depot, pkgs, ... }:
+
+depot.nix.readTree.drvTargets rec {
+  binary = depot.third_party.naersk.buildPackage {
+    src = ./.;
+  };
+
+  image = pkgs.dockerTools.buildLayeredImage {
+    name = "rih-backend";
+    config.Cmd = [ "${binary}/bin/rih-backend" ];
+
+    contents = [
+      binary
+    ];
+  };
+}