b5c90a1e81
Add group.py route, phase4.html template, and supporting state changes. Photos are shown as a flat stream; clicking divider zones inserts entry-break boundaries that split photos into labelled groups. Labels persist via group_labels dict. Done materialises groups into state.groups and advances to write phase. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>