v0.331.0: OnlyOffice opens and saves from FileBrowser and Nextcloud; FileBrowser back at once after a restart (R-1018)

FileBrowser config carries server.internalUrl http://filebrowser:80 (OnlyOffice fetched the public files address and got 403);
Nextcloud's DocumentServerInternalUrl gets its trailing slash (every save was lost: http://onlyoffice:80cache/...);
RestartStack("filebrowser") runs the R-1126 gate at once (files.<domain> was 502 for up to 5 min after the link switched).
Each red-proofed. MinAgent 0.158.1.

controller/internal/infra/infra.go

@@ -459,6 +459,11 @@ func RenderFileBrowserConfigKept(paths []settings.StoragePath, importSource bool
 server:
   port: 80
   baseURL: "/"
+  # R-1018: the address OnlyOffice's server uses to fetch and save a document (FileBrowser's onlyOffice.go builds both
+  # URLs from it at gtstef/filebrowser:1.5.6-stable; it is used by integrations only). Without it FileBrowser hands
+  # OnlyOffice https://files.<domain> — a trip out through the tunnel and back, which failed (403) on demo-hp.
+  # Pinned by TestFileBrowserConfig_R1018_InternalURLIsTheContainer.
+  internalUrl: "http://filebrowser:80"
   # The box updates FileBrowser (the pinned image); a household cannot, so its „An update is available!" is noise.
   # backend/common/settings/structs.go:51 at gtstef/filebrowser:1.5.6-stable (v0.321.0).
   disableUpdateCheck: true