feat: --mode local 一键本地模式 (SQLite + redka, 无需 MySQL/Redis)

- main.go: --mode local 自动配置 db-driver=sqlite, db-name=data/sqlite3.db, redis-driver=redka
- database: 切换纯 Go SQLite 驱动 (github.com/glebarez/sqlite) — 无需 CGO
- docker-compose.yml: backend 添加 MODE=${MODE:-release} env var + data 卷挂载
- run.sh: binary upgrade 默认 --mode local, config.yaml 模板更新为 local 模式
- K8s quick-deploy.yaml: 单容器部署, MODE=local 环境变量切换远程/本地

docker-compose.yml

@@ -60,8 +60,11 @@ services:
     restart: unless-stopped
     ports:
       - "8080:8080"
+    environment:
+      - MODE=${MODE:-release}
     volumes:
       - ./backend/config.yaml:/app/config.yaml
+      - ./backend/data:/app/data
       - /var/run/docker.sock:/var/run/docker.sock
     depends_on:
       mysql: