changes to use mix for publishing via lightpush

.gitignore

@@ -5,3 +5,4 @@ vendor/*
 result
 result/
 cmake-build-*
+lib/

flake.nix

@@ -6,26 +6,35 @@
     nixpkgs.follows = "logos-liblogos/nixpkgs";
     logos-cpp-sdk.url = "github:logos-co/logos-cpp-sdk";
     logos-liblogos.url = "github:logos-co/logos-liblogos";
+    # logos-messaging-nim: branch poc/logos-testnet-mix
+    # Uses git+https (not github:) because the build needs submodules,
+    # and github: type fetches tarballs which don't include submodule content.
+    logos-messaging-nim = {
+      url = "git+https://github.com/logos-messaging/logos-delivery?ref=poc/logos-testnet-mix&submodules=1";
+    };
   };
 
-  outputs = { self, nixpkgs, logos-cpp-sdk, logos-liblogos }:
+  outputs = { self, nixpkgs, logos-cpp-sdk, logos-liblogos, logos-messaging-nim }:
     let
       systems = [ "aarch64-darwin" "x86_64-darwin" "aarch64-linux" "x86_64-linux" ];
       forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f {
         pkgs = import nixpkgs { inherit system; };
         logosSdk = logos-cpp-sdk.packages.${system}.default;
         logosLiblogos = logos-liblogos.packages.${system}.default;
+        logosMessagingNim = (logos-messaging-nim.packages.${system}.libwaku).overrideAttrs (old: {
+          NIMFLAGS = (old.NIMFLAGS or "") + " -d:chronicles_colors:none";
+        });
       });
     in
     {
-      packages = forAllSystems ({ pkgs, logosSdk, logosLiblogos }: 
+      packages = forAllSystems ({ pkgs, logosSdk, logosLiblogos, logosMessagingNim }:
         let
           # Common configuration
           common = import ./nix/default.nix { inherit pkgs logosSdk logosLiblogos; };
           src = ./.;
-          
+
           # Library package (plugin + libwaku)
-          lib = import ./nix/lib.nix { inherit pkgs common src; };
+          lib = import ./nix/lib.nix { inherit pkgs common src logosMessagingNim; };
 
           # Include package (generated headers from plugin)
           include = import ./nix/include.nix { inherit pkgs common src lib logosSdk; };
@@ -47,7 +56,7 @@
         }
       );
 
-      devShells = forAllSystems ({ pkgs, logosSdk, logosLiblogos }: {
+      devShells = forAllSystems ({ pkgs, logosSdk, logosLiblogos, logosMessagingNim }: {
         default = pkgs.mkShell {
           nativeBuildInputs = [
             pkgs.cmake