Introduce `enableUserSignups` runtime setting to allow administrators to control
whether new accounts can be created. Update environment variable and documentation
references to support this feature. UI elements for account creation are now
conditionally rendered based on this flag. Signup attempts are blocked server-side
when disabled, including email, OAuth, and anonymous upgrades.
Add `assertUserSignupAllowed` utility for consistent enforcement and corresponding
unit tests to verify policy behavior.
Implement a check for GitHub OAuth credentials to conditionally render
the GitHub sign-in button. This ensures the UI accurately reflects
available authentication methods based on environment configuration.
- Add `isGithubAuthEnabled` utility to verify server-side credentials
- Propagate GitHub auth status through context providers to the UI
- Conditionally display the GitHub sign-in button in the sign-in page
- Update documentation and examples to use hex encoding for `AUTH_SECRET`
- Add unit tests for the new GitHub authentication configuration logic
- Introduce `USE_ANONYMOUS_AUTH_SESSIONS` to make guest access an opt-in feature.
- Transition root-level pages into `(app)` and `(public)` route groups for improved access control.
- Adopt Figtree as the primary typeface and implement a pre-render theme initialization script.
- Decouple audiobook chapter processing into a standalone API route and harden resource ownership logic.
- Replace the legacy footer with a unified layout and add skeleton loading states for document lists.
- Update environment documentation and test suites to align with the revised routing and auth flows.
BREAKING CHANGE: The audiobook generation API has been restructured, moving specific chapter logic to `/api/audiobook/chapter`.
