feat(15-03): add journal media upload, RSS, and off-by-default Typesense gate

- POST /_journal/api/v1/media/upload requires access_posts and stays under journal/
- Anonymous GET rss is RSS 2.0 honoring rss_* settings; unpublished posts are omitted
- beachcomber Gate reads search_use_typesense (default false) so a fresh save makes no Typesense HTTP

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

plugin.go

@@ -48,7 +48,7 @@ func (p *Plugin) Register(app *backpack.App) error {
 
 func (p *Plugin) Boot(app *backpack.App) error {
 	p.app = app
-	return nil
+	return p.wireSearch(app)
 }
 
 func (p *Plugin) LangFS() fs.FS { return langFS }