Fix financial double-counting, rebuild cashup accountability, and redesign the Reports page

Financial correctness (donation-leg model):
- Donations are no longer mutated when assigned to a registration; assignment now
  creates an immutable "leg" record referencing the original donation instead.
- Fixed several places where money was double-counted once a donation was partially
  or fully assigned (Payments, Revenue summary, Cashup reconciliation, Finance
  report, Profit report, Master Orders, Revenue Detailed).
- Payments now record who recorded them (recordedBy), separate from who they're for.

Cashup:
- Per-user cash denomination counting (optional, any time) replaces the single
  event-wide manual entry; the event's cash actual is the live sum of these counts.
- New "Payment accountability by staff member" breakdown across all methods, and a
  read-only "Report" tab that opens automatically once an event is closed.

Reports page redesign:
- New shell: sidebar of universal filters (events, date range, past/inactive/closed
  toggles), searchable/categorized report grid, and a popup viewer with
  Print/Email/Excel/WhatsApp actions plus an in-app Reporting Guide.
- Visual pass: colored stat tiles and bar charts on most reports, matching mockups.
- PDF exports (download/Print/Email/WhatsApp) now share a branded design mirroring
  the web report — colored header, stat tiles, bar chart, highlighted totals.
- Excel export now produces a styled .xlsx (via exceljs) instead of a plain CSV.
- Master Orders' "Donations made" table is now included in every export channel.

Bug fixes discovered while testing exports:
- Report emails now go through the shared, DB-configurable mail utility instead of
  a one-off transporter that ignored Site Settings SMTP config.
- WhatsApp report sends now surface the actual WAWP API error and auto-recover a
  disconnected session, instead of a bare axios status-code message.

Also: Admin-editable notification preference, richer Admin Registrations dashboard,
{{payment.link}} placeholder for Email/WhatsApp Attendees, and background
email/WhatsApp attendee sending.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/prisma/schema.prisma

@@ -63,6 +63,7 @@ model User {
   notificationPreference NotificationPreference @default(email)
   registrations          Registration[]
   payments               Payment[]
+  paymentsRecorded       Payment[]              @relation("PaymentRecordedBy")
   tickets                Ticket[]
   ticketScans            TicketUsage[]
   passwordResets         PasswordReset[]
@@ -74,6 +75,9 @@ model User {
   eventsReopened   Event[]       @relation("EventReopenedBy")
   cashupsPerformed EventCashup[]
   notifyForEvents  Event[]       @relation("EventNotifyRecipients")
+
+  personCashCountsFor      EventCashupPersonCount[] @relation("EventCashupPersonCountFor")
+  personCashCountsEntered  EventCashupPersonCount[] @relation("EventCashupPersonCountEnteredBy")
 }
 
 model Event {
@@ -112,6 +116,7 @@ model Event {
   reopenedBy   User?         @relation("EventReopenedBy", fields: [reopenedById], references: [id], onDelete: SetNull)
   costs        EventCost[]
   cashups      EventCashup[]
+  personCashCounts EventCashupPersonCount[]
 
   // Users who should receive registration/payment/daily-summary notifications for this
   // event. Falls back to `createdBy` when empty (see backend/src/utils/notifications.js).
@@ -215,6 +220,7 @@ model Payment {
   amount            Float
   method            String
   userId            String
+  recordedById      String?
   registrationId    String?
   eventId           String?
   isDonation        Boolean           @default(false)
@@ -223,6 +229,7 @@ model Payment {
   originalPaymentId String?
   createdAt         DateTime          @default(now())
   user              User              @relation(fields: [userId], references: [id], onDelete: Restrict)
+  recordedBy        User?             @relation("PaymentRecordedBy", fields: [recordedById], references: [id], onDelete: SetNull)
   registration      Registration?     @relation(fields: [registrationId], references: [id], onDelete: SetNull)
   event             Event?            @relation(fields: [eventId], references: [id], onDelete: SetNull)
   originalPayment   Payment?          @relation("SplitPayments", fields: [originalPaymentId], references: [id], onDelete: SetNull)
@@ -230,9 +237,11 @@ model Payment {
   YocoTransaction   YocoTransaction[]
 
   @@index([userId])
+  @@index([recordedById])
   @@index([registrationId])
   @@index([eventId])
   @@index([createdAt])
+  @@index([originalPaymentId])
 }
 
 model Ticket {
@@ -479,6 +488,36 @@ model EventCashupDenomination {
   @@index([lineId])
 }
 
+// Actual physical cash counted for one staff member's recorded cash payments, entered any
+// time (not part of the close flow) purely for accountability — compared against the
+// system-expected amount (computeCashAccountabilityByUser) to show a per-person variance.
+model EventCashupPersonCount {
+  id            String                               @id @default(uuid())
+  eventId       String
+  userId        String
+  enteredById   String?
+  notes         String?
+  createdAt     DateTime                             @default(now())
+  updatedAt     DateTime                             @updatedAt
+  event         Event                                @relation(fields: [eventId], references: [id], onDelete: Cascade)
+  user          User                                 @relation("EventCashupPersonCountFor", fields: [userId], references: [id], onDelete: Cascade)
+  enteredBy     User?                                @relation("EventCashupPersonCountEnteredBy", fields: [enteredById], references: [id], onDelete: SetNull)
+  denominations EventCashupPersonCountDenomination[]
+
+  @@unique([eventId, userId])
+  @@index([eventId])
+}
+
+model EventCashupPersonCountDenomination {
+  id          String                  @id @default(uuid())
+  countId     String
+  value       Float
+  count       Int
+  personCount EventCashupPersonCount  @relation(fields: [countId], references: [id], onDelete: Cascade)
+
+  @@index([countId])
+}
+
 // ─── Church Website Models (disabled — kept for reference, not active Prisma models) ──
 //
 // model Ministry {