feat: 更新 flake.nix ，采用 venv 的方式生成环境，nixos用户也可以本机运行项目了

flake.nix

@@ -1,62 +1,37 @@
 {
   description = "MaiMBot Nix Dev Env";
-  # 本配置仅方便用于开发，但是因为 nb-cli 上游打包中并未包含 nonebot2，因此目前本配置并不能用于运行和调试
 
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11";
-    flake-utils.url = "github:numtide/flake-utils";
+    utils.url = "github:numtide/flake-utils";
   };
 
-  outputs =
-    {
-      self,
-      nixpkgs,
-      flake-utils,
-    }:
-    flake-utils.lib.eachDefaultSystem (
-      system:
-      let
-        pkgs = import nixpkgs {
-          inherit system;
-        };
+  outputs = {
+    self,
+    nixpkgs,
+    utils,
+    ...
+  }:
+    utils.lib.eachDefaultSystem (system: let
+      pkgs = import nixpkgs {inherit system;};
+      pythonPackages = pkgs.python3Packages;
+    in {
+      devShells.default = pkgs.mkShell {
+        name = "python-venv";
+        venvDir = "./.venv";
+        buildInputs = [
+          pythonPackages.python
+          pythonPackages.venvShellHook
+        ];
 
-        pythonEnv = pkgs.python3.withPackages (
-          ps: with ps; [
-            ruff
-            pymongo
-            python-dotenv
-            pydantic
-            jieba
-            openai
-            aiohttp
-            requests
-            urllib3
-            numpy
-            pandas
-            matplotlib
-            networkx
-            python-dateutil
-            APScheduler
-            loguru
-            tomli
-            customtkinter
-            colorama
-            pypinyin
-            pillow
-            setuptools
-          ]
-        );
-      in
-      {
-        devShell = pkgs.mkShell {
-          buildInputs = [
-            pythonEnv
-            pkgs.nb-cli
-          ];
-
-          shellHook = ''
-          '';
-        };
-      }
-    );
-}
+        postVenvCreation = ''
+          unset SOURCE_DATE_EPOCH
+          pip install -r requirements.txt
+        '';
+        
+        postShellHook = ''
+          # allow pip to install wheels
+          unset SOURCE_DATE_EPOCH
+        '';
+      };
+    });
+}