chore: initial commit - Supabase stack with local Docker configuration

configs/env/.env.example

@@ -0,0 +1 @@
+# 放后端开发项目需要的环境变量

configs/flutter/dev.json

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+{
+  "apiBaseUrl": "http://localhost:8000",
+  "environment": "development"
+}

configs/flutter/prod.json

@@ -0,0 +1,4 @@
+{
+  "apiBaseUrl": "https://api.yourdomain.com",
+  "environment": "production"
+}

configs/openapi/openapi.yaml

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+# OpenAPI 规范占位文件
+# 后续通过 FastAPI 自动生成