Add people/face clustering feature

- scripts/cluster_faces.py: greedy centroid clustering (numpy) with 3
  refinement passes; preserves existing UUID/name mappings across re-runs;
  writes MEDIA_ROOT/people.json atomically.
- app.rb: GET /face/* serves cropped+padded face thumbnails (100x100,
  cached under cache/faces/); GET|POST /admin/people for cluster
  management; POST /admin/people/recluster runs cluster_faces.py as a
  background job; POST /admin/people/:uuid saves names+slugs; GET /people
  public grid of named people; GET /people/:slug photos for one person.
- views/admin/people.erb: lists all clusters (named first, then by size),
  face crop samples, inline name form, re-cluster button with live log.
- views/people.erb: public grid of named people.
- views/person.erb: photo grid for one person, linking back to album
  lightbox for each photo.
- views/layout.erb: People link in nav (conditional on FACES_ENABLED).
- public/css/style.css: styles for people admin list and public tiles.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/views/layout.erb b/views/layout.erb
index 086fe8c..e0c5399 100644
--- a/views/layout.erb
+++ b/views/layout.erb
@@ -17,8 +17,10 @@
   <header class="site-header">
     <a href="/browse/" class="site-logo">Albumen</a>
     <nav class="site-nav">
+      <% if FACES_ENABLED %><a href="/people">People</a><% end %>
       <% if admin? %>
         <a href="/admin/edit/<%= defined?(@rel) ? @rel : '' %>">Edit Album</a>
+        <% if FACES_ENABLED %><a href="/admin/people">Manage People</a><% end %>
         <a href="/admin/logout">Logout</a>
       <% else %>
         <a href="/admin/login?return_to=<%= CGI.escape("/admin/edit/#{defined?(@rel) ? @rel : ''}") %>" class="nav-admin">Admin</a>