Add ham radio profile with FLEcli package

Introduces a custom packages overlay (pkgs/) for packages not in nixpkgs.
Adds FLEcli v0.1.7 for processing amateur radio logs (SOTA, POTA, WWFF).
Enables ham-radio profile on beefy.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkgs/default.nix

@@ -0,0 +1,7 @@
+# ABOUTME: Custom packages overlay for packages not in nixpkgs.
+# ABOUTME: Adds packages under pkgs.custom.* namespace.
+final: prev: {
+  custom = {
+    flecli = final.callPackage ./flecli.nix { };
+  };
+}