feat(crm): frontend code — pages + services + components

Brings in the full frontend CRM stack: admin authoring pages,
customer-portal surfaces, public response flows, typed services,
and the supporting component library. i18n locale JSON is the next
commit (kept separate so reviewers can read it as data).

Pages
  - Quotes: list / editor / detail / public accept-decline
  - Invoices: list / editor / detail / public payment-check
  - Contracts: list / editor / detail / block library / public sign
  - Calendar (FullCalendar — admin-only v1)
  - Tax report (period picker + CSV/PDF export)
  - Hours (logged time entries, per-customer)
  - Deals lineage (DocumentLineageCard surfaces)
  - CRM Development (admin dev tools, gated by crmDevelopment flag)
  - Customer-portal pages for quotes / invoices / contracts
  - Settings reorg: CRM-Settings group + dedicated tabs for Business
    Profile, CRM behaviour, Contracts block library, Reminder emails
  - BrandingPage typography (PDF font picker)
  - EventDetailsPage / CustomerDetailPage / CreateEventPage extensions
    (event-time fields, hours toggle, per-event reminder override)

Services (typed)
  - quotes.service, bills.service, contracts.service
  - customerAdmin.service, deals.service, calendar.service,
    taxReport.service, contracts-blocks.service
  - businessProfile.service (timezone, font picker, bank accounts)
  - useInstallmentDefaults hook, useLocalizedDate dateInputLang extension

Components (admin)
  - CustomerPicker (shared across quote/invoice/contract editors)
  - LineItemsTable (hierarchy + details_text, memoised pricing)
  - InstallmentsPanel (simple + advanced toggle, fixed-date vs trigger)
  - DocumentLineageCard (deal_uuid grouped view)
  - EditInstallmentPlanModal (atomic post-spawn plan reshape)
  - EventReminderOverrideCard, EmailTemplateEditor (tiptap),
    PdfFontPicker, IntegrityCheckCard
  - Feature-flag context + RequireFeature wrapper + AdminSidebar
    featureFlagsAny derivation + UI-hiding sweep

Build infra
  - vite.config: fullcalendar chunk carved off (~200 KB lazy-loaded)
  - frontend/package.json: tiptap, fullcalendar, signature_pad,
    react-international-phone, et al.
  - tailwind + prose styles updated for editor surfaces

3-way merge note: 1 conflict (CustomerDetailPage.tsx) hand-resolved
to keep upstream's SUPPORTED_LANGUAGES.map() data-driven pattern
over feat/crm's hardcoded option list; feat/crm's DecimalInput
import preserved alongside.

frontend/vite.config.ts

@@ -14,6 +14,17 @@ const config: VitestUserConfig = {
         manualChunks: {
           'react-vendor': ['react', 'react-dom', 'react-router-dom'],
           'ui-vendor': ['lucide-react', 'react-toastify'],
+          // Migration 137 — admin calendar deps (~200 KB). Carved into
+          // their own chunk so the main bundle isn't penalised on
+          // every page load; the calendar route lazy-loads this chunk
+          // on demand via React.lazy.
+          'fullcalendar': [
+            '@fullcalendar/react',
+            '@fullcalendar/core',
+            '@fullcalendar/daygrid',
+            '@fullcalendar/timegrid',
+            '@fullcalendar/interaction',
+          ],
         },
       },
     },