[grade=B] feat(auth): onboard missing credentials into encrypted vault

dashcaddy-installer/install.sh

@@ -630,10 +630,15 @@ generate_caddyfile() {
 SNIP
 
   local auth_snippet="(dashcaddy_auth) {
-  forward_auth localhost:${API_PORT} {
+  @needsAuth not path /dashcaddy-sso
+  forward_auth @needsAuth localhost:${API_PORT} {
     uri /api/v1/auth/gate/{args[0]}
     copy_headers Authorization X-Api-Key X-App-Cookie X-Emby-Token X-Plex-Token
   }
+  handle /dashcaddy-sso {
+    rewrite * /api/v1/auth/sso-exchange
+    reverse_proxy localhost:${API_PORT}
+  }
 }"
 
   local site_body="  root * ${DASHBOARD_DIR}