feat: Projects + stronger LLM placeholder substitution

Backend:
- Project model with defaults: defaultClient, defaultTemplate, defaultBankAccount
- Document gets optional projectId (FK + index)
- Migration 2_projects: enum ProjectStatus + Project table + Document.projectId
- API: /api/projects CRUD, GET /api/projects/:id/documents
- documents/routes filter by projectId

LLM prompt:
- Concrete preamble example: «ООО «...», в лице директора ... , ИП ..., ОГРНИП ...»
  → {{customer.name}}, {{customer.signatoryPosition}} {{customer.signatoryName}},
    {{executor.name}}, {{executor.ogrn}}
- Expanded placeholder list (signatoryName/Position для customer, ogrn etc)
- Side-role detection: «Заказчик» vs «Исполнитель» map to customer/executor

Frontend:
- /projects (list) and /projects/:id (defaults form + documents list under project)
- Nav: «Проекты» first
- DocumentEdit reads projectId from URL, presets default client from project,
  saves projectId with the document

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/prisma/schema.prisma

@@ -55,6 +55,12 @@ enum PaymentKind {
   outgoing
 }
 
+enum ProjectStatus {
+  active
+  completed
+  cancelled
+}
+
 model Organization {
   id           String   @id @default(uuid()) @db.Uuid
   name         String
@@ -82,6 +88,31 @@ model Organization {
   tochkaCredentials TochkaCredential[]
   auditLog         AuditLog[]
   bankAccounts     BankAccount[]
+  projects         Project[]
+}
+
+model Project {
+  id                    String   @id @default(uuid()) @db.Uuid
+  organizationId        String   @db.Uuid
+  organization          Organization @relation(fields: [organizationId], references: [id], onDelete: Cascade)
+  name                  String
+  status                ProjectStatus @default(active)
+  // Дефолты — подставляются при создании документов внутри проекта
+  defaultClientId       String?  @db.Uuid
+  defaultClient         Client?  @relation(fields: [defaultClientId], references: [id])
+  defaultTemplateId     String?  @db.Uuid
+  defaultTemplate       DocumentTemplate? @relation(fields: [defaultTemplateId], references: [id])
+  defaultBankAccountId  String?  @db.Uuid
+  defaultBankAccount    BankAccount? @relation(fields: [defaultBankAccountId], references: [id])
+  notes                 String?
+  archivedAt            DateTime?
+  createdAt             DateTime @default(now())
+  updatedAt             DateTime @updatedAt
+
+  documents Document[]
+
+  @@index([organizationId, archivedAt])
+  @@index([organizationId, status])
 }
 
 model BankAccount {
@@ -100,6 +131,7 @@ model BankAccount {
   updatedAt       DateTime @updatedAt
 
   tochkaCredentials TochkaCredential[]
+  defaultForProjects Project[]
 
   @@index([organizationId])
 }
@@ -121,6 +153,7 @@ model Client {
   updatedAt      DateTime   @updatedAt
 
   documents Document[]
+  defaultForProjects Project[]
 
   @@index([organizationId])
   @@index([organizationId, name])
@@ -155,6 +188,8 @@ model DocumentTemplate {
   createdAt      DateTime @default(now())
   updatedAt      DateTime @updatedAt
 
+  defaultForProjects Project[]
+
   @@index([organizationId, docType])
 }
 
@@ -162,6 +197,8 @@ model Document {
   id                 String     @id @default(uuid()) @db.Uuid
   organizationId     String     @db.Uuid
   organization       Organization @relation(fields: [organizationId], references: [id])
+  projectId          String?    @db.Uuid
+  project            Project?   @relation(fields: [projectId], references: [id])
   docType            DocType
   number             String
   issuedAt           DateTime?
@@ -188,6 +225,7 @@ model Document {
   @@unique([organizationId, docType, number])
   @@index([organizationId, clientId, issuedAt(sort: Desc)])
   @@index([organizationId, status])
+  @@index([organizationId, projectId])
   @@index([tochkaDocumentId])
 }