feat: opaque session、安装/发帖 SSR 与最小 Admin 后台

浏览器登录改为 DB sessions（可吊销）；敏感词与 OIDC PEM 入 settings；
落地安装向导、注册发帖与 /admin 仪表盘/板块/审核/设置。

Co-authored-by: Cursor <cursoragent@cursor.com>

services/compose_body.go

@@ -0,0 +1,97 @@
+package services
+
+import (
+	"html"
+	"regexp"
+	"strings"
+)
+
+var (
+	mdImageRe = regexp.MustCompile(`!\[([^\]]*)\]\(([^)]+)\)`)
+	mdLinkRe  = regexp.MustCompile(`\[([^\]]+)\]\(([^)]+)\)`)
+)
+
+// ComposeBodyToHTML 将发帖表单正文转为可消毒 HTML。
+// 若已含块级 HTML 标签则原样交 Sanitize；否则按纯文本/轻量 Markdown 转段落。
+func ComposeBodyToHTML(raw string) string {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return ""
+	}
+	lower := strings.ToLower(raw)
+	if strings.Contains(lower, "<p") || strings.Contains(lower, "<div") ||
+		strings.Contains(lower, "<h1") || strings.Contains(lower, "<ul") ||
+		strings.Contains(lower, "<ol") || strings.Contains(lower, "<pre") ||
+		strings.Contains(lower, "<blockquote") {
+		return raw
+	}
+
+	// 先转义，再恢复轻量 md 图片/链接
+	esc := html.EscapeString(raw)
+	esc = mdImageRe.ReplaceAllStringFunc(esc, func(m string) string {
+		sub := mdImageRe.FindStringSubmatch(m)
+		if len(sub) != 3 {
+			return m
+		}
+		alt, src := sub[1], sub[2]
+		// 仅允许站内 uploads 或 http(s)
+		if !safeComposeURL(src) {
+			return m
+		}
+		return `<p><img src="` + html.EscapeString(src) + `" alt="` + alt + `"></p>`
+	})
+	esc = mdLinkRe.ReplaceAllStringFunc(esc, func(m string) string {
+		sub := mdLinkRe.FindStringSubmatch(m)
+		if len(sub) != 3 {
+			return m
+		}
+		text, href := sub[1], sub[2]
+		if !safeComposeURL(href) {
+			return m
+		}
+		return `<a href="` + html.EscapeString(href) + `" rel="noopener noreferrer">` + text + `</a>`
+	})
+
+	parts := strings.Split(esc, "\n\n")
+	var b strings.Builder
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p == "" {
+			continue
+		}
+		// 已是独立 img 段
+		if strings.HasPrefix(p, "<p><img ") {
+			b.WriteString(p)
+			continue
+		}
+		p = strings.ReplaceAll(p, "\n", "<br>\n")
+		b.WriteString("<p>")
+		b.WriteString(p)
+		b.WriteString("</p>\n")
+	}
+	return b.String()
+}
+
+func safeComposeURL(u string) bool {
+	u = strings.TrimSpace(u)
+	if strings.HasPrefix(u, "/uploads/") || strings.HasPrefix(u, "/media/") {
+		return true
+	}
+	return strings.HasPrefix(u, "https://") || strings.HasPrefix(u, "http://")
+}
+
+// HTMLToComposePlain 编辑页回显：去掉简单标签便于 textarea 编辑（尽力而为）
+func HTMLToComposePlain(htmlBody string) string {
+	s := strings.TrimSpace(htmlBody)
+	if s == "" {
+		return ""
+	}
+	// img → markdown
+	imgRe := regexp.MustCompile(`(?i)<img[^>]+src="([^"]+)"[^>]*>`)
+	s = imgRe.ReplaceAllString(s, "![]($1)")
+	s = regexp.MustCompile(`(?i)</p>\s*<p>`).ReplaceAllString(s, "\n\n")
+	s = regexp.MustCompile(`(?i)<br\s*/?>`).ReplaceAllString(s, "\n")
+	s = regexp.MustCompile(`(?i)</?p[^>]*>`).ReplaceAllString(s, "")
+	s = regexp.MustCompile(`(?i)<[^>]+>`).ReplaceAllString(s, "")
+	return strings.TrimSpace(html.UnescapeString(s))
+}