feat(generator): add -default-view to choose timeline or grid as site root

The chosen view is published at /, the other under /timeline/ or
/grid/. Page paths, pager links and the cross-links between the views
are derived from the setting. The directory named after the default
view is removed on build, since it can only be a leftover from before
a switch.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -101,6 +101,8 @@ nix-shell -p apacheHttpd --run \
 | `fontsURL`                  | Crimson Pro + Manjari              | Stylesheet URL loading both web fonts |
 | `serifFamily`               | `Crimson Pro`                      | CSS font-family for the primary serif |
 | `mlFamily`                  | `Manjari`                          | CSS font-family for the alt-script bio |
+| `pageSize`                  | `60`                               | Photos per page on the timeline and grid views |
+| `defaultView`               | `timeline`                         | View at the site root, `timeline` or `grid`; the other is served under `/timeline/` or `/grid/` |
 | `nginx.enable`              | `false`                            | Configure an nginx vhost             |
 | `nginx.domain`              | —                                  | Domain for the vhost                 |
 | `nginx.htpasswdFile`        | —                                  | htpasswd file for `/upload` and `/manage` |