Sovran_Bitcoin 0.15.12 serves the RTL UI under /rtl/ (upstream Angular
<base href="/rtl/"> + PathLocationStrategy); the package redirects / to
/rtl/ only for the exact root path.
Update the Hub's RTL tile so the Tor and Local Network credentials show
the canonical /rtl/ URLs (with trailing slash, which the redirect does
not cover) instead of relying on the root-path redirect. Bump the dev
versions.json fallback for rtl.service from 0.15.10 to 0.15.12 to match
the flake (deployed systems already read pkgs.sovran-bitcoin.rtl.version).