The template was removed from the template map and is no longer
rendered, but the file was still on disk and embedded via
//go:embed *.html. Remove it to complete the cleanup.
/ now checks for an authenticated session:
- Authenticated users → 303 redirect to /sources
- Unauthenticated users → 303 redirect to /pages/login
Removes the old index page template rendering and formatUptime
helper (now dead code). Adds tests for both redirect cases.