Add deal co-assignees and saved filters on people/pipeline lists.

Deals keep a primary owner plus shared assignees with matching visibility; Contacts and Pipeline can save and reuse filter presets.

apps/api/prisma/schema.prisma

@@ -224,6 +224,7 @@ model User {
   organizationId String
   organization   Organization @relation(fields: [organizationId], references: [id], onDelete: Cascade)
   ownedDeals     Deal[]       @relation("DealOwner")
+  assignedDeals  Deal[]       @relation("DealAssignees")
   ownedQuotes    Quote[]      @relation("QuoteOwner")
   ownedInvoices  Invoice[]    @relation("InvoiceOwner")
   ownedPeople    Person[]     @relation("PersonOwner")
@@ -509,6 +510,7 @@ model Deal {
   company        Company?        @relation(fields: [companyId], references: [id], onDelete: SetNull)
   ownerId        String?
   owner          User?           @relation("DealOwner", fields: [ownerId], references: [id], onDelete: SetNull)
+  assignees      User[]          @relation("DealAssignees")
   position       Int             @default(0)
   activities     Activity[]
   smartNotes     Note[]