feat: OpsxDB 桌面数据库客户端首版入库

含工作台/连库多引擎字段与 SSH·SSL、结果编辑、Redis 键浏览、
Tauri 桌面与 docs/落地页；排除本地构建产物与 sidecar 二进制。

apps/server/internal/site/site.go

@@ -0,0 +1,58 @@
+// Package site：产品官网落地页（嵌入二进制，深色密度跟工作台）。
+package site
+
+import (
+	"embed"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+//go:embed template.html assets
+var files embed.FS
+
+type Handler struct {
+	html string
+}
+
+func New() *Handler {
+	raw, err := files.ReadFile("template.html")
+	if err != nil {
+		panic("site: template.html 缺失: " + err.Error())
+	}
+	return &Handler{html: string(raw)}
+}
+
+func (h *Handler) Register(r *gin.Engine) {
+	r.GET("/", h.Page)
+	r.GET("/home", h.Page)
+	r.GET("/index.html", h.Page)
+	r.GET("/site/assets/*file", h.Asset)
+}
+
+func (h *Handler) Page(c *gin.Context) {
+	c.Header("Content-Type", "text/html; charset=utf-8")
+	c.Header("Cache-Control", "no-cache")
+	_, _ = c.Writer.WriteString(h.html)
+}
+
+func (h *Handler) Asset(c *gin.Context) {
+	name := strings.TrimPrefix(c.Param("file"), "/")
+	if strings.Contains(name, "..") {
+		c.Status(http.StatusBadRequest)
+		return
+	}
+	data, err := files.ReadFile("assets/" + name)
+	if err != nil {
+		c.Status(http.StatusNotFound)
+		return
+	}
+	ct := "application/octet-stream"
+	if strings.HasSuffix(name, ".css") {
+		ct = "text/css; charset=utf-8"
+	}
+	c.Header("Content-Type", ct)
+	c.Header("Cache-Control", "public, max-age=3600")
+	c.Data(http.StatusOK, ct, data)
+}