feat: add Nix development environment with flake support

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -55,4 +55,8 @@ test-reports
 # Cursor specific
 .cursor/
 build/
-target/
+target/
+
+# Nix specific
+.direnv
+.nix-store

Makefile

@@ -1088,4 +1088,4 @@ mod-tidy: ## Run go mod tidy on modules (Usage: make mod-tidy [MODULE=all|core|p
 		done; \
 	fi
 	@echo ""
-	@echo "$(GREEN)✓ go mod tidy complete$(NC)"
+	@echo "$(GREEN)✓ go mod tidy complete$(NC)"

flake.nix

@@ -0,0 +1,92 @@
+{
+  description = "Bifrost's Nix Flake";
+
+  # Flake inputs
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/staging-next";
+  };
+
+  # Flake outputs
+  outputs = {self, ...} @ inputs: let
+    # The systems supported for this flake's outputs
+    supportedSystems = [
+      "x86_64-linux" # 64-bit Intel/AMD Linux
+      "aarch64-linux" # 64-bit ARM Linux
+      "aarch64-darwin" # 64-bit ARM macOS
+    ];
+
+    # Helper for providing system-specific attributes
+    forEachSupportedSystem = f:
+      inputs.nixpkgs.lib.genAttrs supportedSystems (
+        system:
+          f {
+            inherit system;
+            # Provides a system-specific, configured Nixpkgs
+            pkgs = import inputs.nixpkgs {
+              inherit system;
+              # Enable using unfree packages
+              config.allowUnfree = true;
+            };
+          }
+      );
+  in {
+    # To activate the default environment:
+    # nix develop
+    # Or if you use direnv:
+    # direnv allow
+    devShells = forEachSupportedSystem (
+      {
+        pkgs,
+        system,
+      }: {
+        # Run `nix develop` to activate this environment or `direnv allow` if you have direnv installed
+        default = pkgs.mkShellNoCC {
+          # The name of the environment
+          name = "bifrost-nix-dev-shell";
+
+          # The Nix packages provided in the environment
+          packages = with pkgs; [
+            go
+            gopls
+            gofumpt
+            air
+            delve # provides dlv
+            go-tools # provides staticcheck
+
+            nodejs_24
+          ];
+
+          # Set any environment variables for your development environment
+          env = {};
+
+          # Add any shell logic you want executed when the environment is activated
+          shellHook = ''
+            ##
+            ## Go: project-local GOPATH/GOBIN
+            ##
+            export GOPATH="$PWD/.nix-store/go"
+            export GOBIN="$GOPATH/bin"
+            export GOMODCACHE="$GOPATH/pkg/mod"
+            export GOCACHE="$PWD/.nix-store/gocache"
+
+            mkdir -p "$GOBIN" "$GOMODCACHE" "$GOCACHE"
+
+            export PATH="$PATH:$GOBIN"
+
+            ##
+            ## Node: project-local "global" npm prefix
+            ##
+            # npm reads npm_config_prefix (or NPM_CONFIG_PREFIX) as the "prefix" config,
+            # which is where `npm i -g` installs to.
+            export npm_config_prefix="$PWD/.nix-store/npm-global"
+
+            mkdir -p "$npm_config_prefix/bin"
+
+            # Ensure "global" npm bin is on PATH for this shell only
+            export PATH="$PATH:$npm_config_prefix/bin"
+          '';
+        };
+      }
+    );
+  };
+}