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)

backend/scripts/migrate.sh

@@ -6,17 +6,16 @@
 set -e
 
 MIGRATIONS_DIR="./migrations"
-DB_HOST="${POSTGRES_HOST:-localhost}"
-DB_PORT="${POSTGRES_PORT:-5432}"
-DB_NAME="${POSTGRES_DATABASE:-gochat_dev}"
-DB_USER="${POSTGRES_USERNAME:-postgres}"
-DB_PASS="${POSTGRES_PASSWORD:-}"
-
-DSN="postgres://${DB_USER}:${DB_PASS}@${DB_HOST}:${DB_PORT}/${DB_NAME}?sslmode=disable"
+DSN="${GOCHAT_DATABASE_DSN:-postgres://postgres:postgres@localhost:5432/gochat_dev?sslmode=disable}"
 
 case "$1" in
   create)
-    echo "Creating database ${DB_NAME}..."
+    echo "Creating database from DSN..."
+    # Extract dbname from DSN for createdb
+    DB_NAME=$(echo "$DSN" | sed 's|.*/||; s|\?.*||')
+    DB_HOST=$(echo "$DSN" | sed 's|.*@||; s|:.*||')
+    DB_PORT=$(echo "$DSN" | sed 's|.*@.*:||; s|/.*||')
+    DB_USER=$(echo "$DSN" | sed 's|.*://||; s|:.*||')
     createdb -h "${DB_HOST}" -p "${DB_PORT}" -U "${DB_USER}" "${DB_NAME}" 2>/dev/null || echo "Database already exists"
     ;;
   up)