feat(awgen): add AmneziaWG configuration generator package

Package alex/awgen (offline, stateless Rust CLI for AmneziaWG configs) from
the upstream Gitea repository. Source is fetched with fetchFromGitea and
pinned to the v0.1 tag; the cargo dependency hash is pinned as well.

Also list the package in the README package table and project tree.

packages/awgen/default.nix

@@ -0,0 +1,5 @@
+{
+  pkgs,
+  ...
+}:
+pkgs.callPackage ./package.nix { }

packages/awgen/package.nix

@@ -0,0 +1,38 @@
+{
+  lib,
+  rustPlatform,
+  fetchFromGitea,
+}:
+
+rustPlatform.buildRustPackage rec {
+  pname = "awgen";
+  version = "0.1";
+
+  src = fetchFromGitea {
+    domain = "git.millerson.name";
+    owner = "alex";
+    repo = "awgen";
+    rev = "v${version}";
+    hash = "sha256-PTwOswKI08/oHTKZDZOQfPPBXhNNxot2+tpnUweZ8gg=";
+  };
+
+  cargoHash = "sha256-/ENWhp2SpcZcTk55xXsm/IHfyj86aNzH6PAb9VBtAX4=";
+
+  passthru = {
+    category = "Networking";
+    updateScript = [
+      "nix-update"
+      "--flake"
+      "awgen"
+    ];
+  };
+
+  meta = with lib; {
+    description = "Offline, stateless CLI for AmneziaWG configurations — harmonises native .conf and vpn:// inputs, generates client participants and tunnels, and analyses obfuscation";
+    homepage = "https://git.millerson.name/alex/awgen";
+    changelog = "https://git.millerson.name/alex/awgen/commits/tag/v${version}";
+    license = licenses.mit;
+    mainProgram = "awgen";
+    platforms = platforms.unix;
+  };
+}