feat(treasury): show who still owes on the finance pages

Partial receipts and payments stay tied to a customer, company, or user, and the open balance is listed on the income and expense screens.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/prisma/schema.prisma

@@ -295,6 +295,7 @@ model User {
   ownedInvoices          Invoice[]                @relation("InvoiceOwner")
   ownedPeople            Person[]                 @relation("PersonOwner")
   ownedCompanies         Company[]                @relation("CompanyOwner")
+  financialPartyDocuments FinancialDocument[]     @relation("FinancialDocumentParty")
   ownedProjectCards      ProjectCard[]            @relation("ProjectCardOwner")
   activities             Activity[]               @relation("ActivityAssignee")
   assignedActivities     Activity[]               @relation("ActivityAssignees")
@@ -524,6 +525,7 @@ model Company {
   customFields       Json          @default("{}")
   groupLinks         CompanyGroupLink[]
   people             Person[]
+  financialDocuments FinancialDocument[]
   deals              Deal[]
   activities         Activity[]
   smartNotes         Note[]
@@ -2330,6 +2332,12 @@ model FinancialDocument {
   category       FinancialCategory?   @relation(fields: [categoryId], references: [id], onDelete: SetNull)
   personId       String?
   person         Person?              @relation(fields: [personId], references: [id], onDelete: SetNull)
+  companyId      String?
+  company        Company?             @relation(fields: [companyId], references: [id], onDelete: SetNull)
+  userId         String?
+  partyUser      User?                @relation("FinancialDocumentParty", fields: [userId], references: [id], onDelete: SetNull)
+  /// person | company | user | other
+  partyKind      String?
   partyName      String?
   accountId      String?
   account        FinancialAccount?    @relation("DocumentAccount", fields: [accountId], references: [id], onDelete: SetNull)
@@ -2350,6 +2358,8 @@ model FinancialDocument {
   @@index([organizationId, kind, bookedAt])
   @@index([organizationId, status])
   @@index([personId])
+  @@index([companyId])
+  @@index([userId])
 }
 
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