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/src/features/settings/hooks/useSettingsState.ts

@@ -25,6 +25,11 @@ export interface GeneralSettings {
   use_original_filenames_for_downloads: boolean;
   default_language: string;
   date_format: { format: string; locale: string };
+  /** '12h' or '24h' — controls how times are RENDERED across admin
+   *  + customer-facing views (formatDateTime / formatTime). The
+   *  underlying storage is always HH:mm (24h); only the visual
+   *  presentation toggles. Default '24h' (operator's locale). */
+  time_format: '12h' | '24h';
 }
 
 export interface SecuritySettings {
@@ -101,7 +106,8 @@ export function useSettingsState() {
     short_gallery_urls: false,
     use_original_filenames_for_downloads: false,
     default_language: 'en',
-    date_format: { format: 'dd/MM/yyyy', locale: 'en-GB' }
+    date_format: { format: 'dd/MM/yyyy', locale: 'en-GB' },
+    time_format: '24h'
   });
 
   // Security settings state
@@ -192,7 +198,8 @@ export function useSettingsState() {
           ? (typeof settings.general_date_format === 'string'
               ? { format: settings.general_date_format, locale: settings.general_date_format.includes('MM/dd') ? 'en-US' : 'en-GB' }
               : settings.general_date_format)
-          : { format: 'dd/MM/yyyy', locale: 'en-GB' }
+          : { format: 'dd/MM/yyyy', locale: 'en-GB' },
+        time_format: settings.general_time_format === '12h' ? '12h' : '24h'
       });
 
       setSecuritySettings({