fix(content-gen): strip URLs and site-list sections from generated content

Forbid URLs/domains/markdown links across prompt rules (runtime, platform
templates, outline/imitation/title flows) and rename "官网" placeholder to
"官网信息" with explicit instructions that links are background only.
Add sanitizeGeneratedArticleMarkdown to strip URLs, HTML images, and
"网站列表/官网列表" labels from LLM output, wired into article, prompt-rule,
template, and outline generation. Drop the site_list outline section seed
and filter blocked outline keys in the wizard so stored drafts cannot
resurrect it.

server/internal/tenant/app/template_assist.go

@@ -1222,7 +1222,7 @@ func normalizeOutlineNodes(nodes []OutlineNode, depth int) []OutlineNode {
 
 	items := make([]OutlineNode, 0, len(nodes))
 	for _, node := range nodes {
-		outline := strings.TrimSpace(node.Outline)
+		outline := sanitizeGeneratedOutlineText(node.Outline)
 		if outline == "" {
 			continue
 		}