fix(caddy): serve launcher from sibling mount, not nested under /srv/www

Mounting ./mirror/launcher at /srv/www/launcher failed: /srv/www is a
read-only mount, so the nested mountpoint can't be created. Mount it at
/srv/launcher and route /launcher/* via handle_path instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

caddy/Caddyfile

@@ -7,8 +7,17 @@
 }
 
 http://{$BASE_DOMAIN} {
-	root * /srv/www
-	file_server
+	# Launcher downloads live in a sibling mount (not nested under /srv/www,
+	# which is a read-only mount → can't create a nested mountpoint).
+	# handle_path strips the /launcher prefix before serving /srv/launcher.
+	handle_path /launcher/* {
+		root * /srv/launcher
+		file_server browse
+	}
+	handle {
+		root * /srv/www
+		file_server
+	}
 }
 
 http://auth.{$BASE_DOMAIN} {