Implements the full User Connections & Notification Centre feature:
Phase 1 - Database: migrations 039-043 adding umbral_name to users,
profile/social fields to settings, notifications table, connection
request/user_connection tables, and linked_user_id to people.
Phase 2 - Notifications: backend CRUD router + service + 90-day purge,
frontend NotificationsPage with All/Unread filter, bell icon in sidebar
with unread badge polling every 60s.
Phase 3 - Settings: profile fields (phone, mobile, address, company,
job_title), social card with accept_connections toggle and per-field
sharing defaults, umbral name display with CopyableField.
Phase 4 - Connections: timing-safe user search, send/accept/reject flow
with atomic status updates, bidirectional UserConnection + Person records,
in-app + ntfy notifications, per-receiver pending cap, nginx rate limiting.
Phase 5 - People integration: batch-loaded shared profiles (N+1 prevention),
Ghost icon for umbral contacts, Umbral filter pill, split Add Person button,
shared field indicators (synced labels + Lock icons), disabled form inputs
for synced fields on umbral contacts.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
