refactor: 统一 DB/Redis 配置为 DSN 模式 + 移除 Helm/K8s 部署

- DatabaseConfig: Host/Port/User/Password/Name/DBName/SSLMode → 单个 DSN 字段
- RedisConfig: Host/Port/Password/DB/URL → 单个 DSN 字段
- 环境变量: GOCHAT_DATABASE_* (7个) → GOCHAT_DATABASE_DSN, GOCHAT_REDIS_* (5个) → GOCHAT_REDIS_DSN
- validator.go: DSN URL 解析校验 (scheme + host)
- redis.go: redis.ParseURL(cfg.DSN) 直连
- 所有 docker-compose / CI / shell 脚本 / .env 同步更新
- 删除 deploy/helm/ 整个目录 (20个文件)
- CI 删除 helm-validate / deploy-staging / deploy-production 三个 job
- 文档同步更新 (README, 架构设计, PRD, 滚动升级)

deploy/quickstart/compose.yaml

@@ -80,17 +80,10 @@ services:
       GOCHAT_SERVER_HOST: 0.0.0.0
       GOCHAT_SERVER_PORT: 3000
       GOCHAT_SERVER_MODE: ${GOCHAT_SERVER_MODE:-debug}
-      GOCHAT_DATABASE_HOST: postgres
-      GOCHAT_DATABASE_PORT: 5432
-      GOCHAT_DATABASE_USER: ${POSTGRES_USER:-gochat}
-      GOCHAT_DATABASE_PASSWORD: ${POSTGRES_PASSWORD:-gochat_dev}
-      GOCHAT_DATABASE_DBNAME: ${POSTGRES_DB:-gochat_dev}
-      GOCHAT_DATABASE_SSLMODE: disable
+      GOCHAT_DATABASE_DSN: postgres://${POSTGRES_USER:-gochat}:${POSTGRES_PASSWORD:-gochat_dev}@postgres:5432/${POSTGRES_DB:-gochat_dev}?sslmode=disable
       GOCHAT_DATABASE_RUN_MIGRATIONS: "true"
       GOCHAT_DATABASE_MIGRATIONS_PATH: /app/migrations
-      GOCHAT_REDIS_HOST: redis
-      GOCHAT_REDIS_PORT: 6379
-      GOCHAT_REDIS_PASSWORD: ${REDIS_PASSWORD:-}
+      GOCHAT_REDIS_DSN: ${REDIS_DSN:-redis://redis:6379}
       GOCHAT_REDIS_POOL_SIZE: 50
       GOCHAT_SEARCH_ENGINE: meilisearch
       GOCHAT_SEARCH_HOST: http://meilisearch:7700