feat: 可选社区上报与官方精选展柜

默认关闭，仪表盘一键开关；枢纽由运维配置收报，人工精选后展示于 /showcase。

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

service/ratelimit.go

@@ -54,6 +54,9 @@ func (r *RateLimiter) limitFor(action string) int {
 	if action == "friend_link" {
 		return 5
 	}
+	if action == "community_heartbeat" {
+		return 30
+	}
 	return r.settings.RateLimitFor(action)
 }
 
@@ -61,6 +64,9 @@ func (r *RateLimiter) windowFor(action string) time.Duration {
 	if action == "friend_link" {
 		return time.Hour
 	}
+	if action == "community_heartbeat" {
+		return time.Hour
+	}
 	return time.Duration(r.settings.RateLimitWindowSec()) * time.Second
 }