chore(dev): 配置本地开发环境

引入 devenv 与 starship 配置，统一 Go/Node/Postgres 开发依赖与快捷命令。
同时让脚本在使用本地数据库环境时跳过 Docker 创建步骤。

devenv.yaml

@@ -0,0 +1,18 @@
+# yaml-language-server: $schema=https://devenv.sh/devenv.schema.json
+inputs:
+  nixpkgs:
+    url: github:cachix/devenv-nixpkgs/rolling
+
+# If you're using non-OSS software, you can set allowUnfree to true.
+# allowUnfree: true
+
+# If you're not willing to allow unsupported packages:
+# allowUnsupportedSystem: false
+
+# If you're willing to use a package that's vulnerable
+# permittedInsecurePackages:
+#  - "openssl-1.1.1w"
+
+# If you have more than one devenv you can merge them
+#imports:
+# - ./backend