Add lessons module, rate cycles, EC2 deploy scripts, and help content

- Lessons module: lesson types, instructors, schedule slots, enrollments,
  sessions (list + week grid view), lesson plans, grading scales, templates
- Rate cycles: replace monthly_rate with billing_interval + billing_unit on
  enrollments; add weekly/monthly/quarterly rate presets to lesson types and
  schedule slots with auto-fill on enrollment form
- Member detail page: tabbed layout for details, identity documents, enrollments
- Sessions week view: custom 7-column grid replacing react-big-calendar
- Music store seed: instructors, lesson types, slots, enrollments, sessions,
  grading scale, lesson plan template
- Scrollbar styling: themed to match sidebar/app palette
- deploy/: EC2 setup and redeploy scripts, nginx config, systemd service
- Help: add Lessons category (overview, types, instructors, slots, enrollments,
  sessions, plans/grading); collapsible sidebar with independent scroll;
  remove POS/accounting references from docs

deploy/lunarfront.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=LunarFront API Server
+After=network.target postgresql.service
+
+[Service]
+Type=simple
+User=ubuntu
+WorkingDirectory=/opt/lunarfront/packages/backend
+EnvironmentFile=/opt/lunarfront/.env
+ExecStart=/home/ubuntu/.bun/bin/bun run src/main.ts
+Restart=always
+RestartSec=5
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=lunarfront
+
+[Install]
+WantedBy=multi-user.target