feature: a very minimal patients feature implemented. it needs lots of improvments though

backend/prisma/schema.prisma

@@ -55,6 +55,7 @@ model Organization {
 
   sharedWithMe     OrganizationLink[] @relation("OrganizationB")
   sharedWithOthers OrganizationLink[] @relation("OrganizationA")
+  patients         Patient[]
 
   createdAt DateTime @default(now())
   updatedAt DateTime @updatedAt
@@ -62,6 +63,45 @@ model Organization {
   @@map("organizations")
 }
 
+model Patient {
+  id             String   @id @default(uuid())
+  organizationId String
+  firstName      String
+  lastName       String
+  phone          String?
+  email          String?
+  dateOfBirth    DateTime?
+  notes          String?
+  isActive       Boolean  @default(true)
+  createdAt      DateTime @default(now())
+  updatedAt      DateTime @updatedAt
+
+  organization Organization             @relation(fields: [organizationId], references: [id])
+  treatments   PatientTreatmentHistory[]
+
+  @@index([organizationId, createdAt])
+  @@index([organizationId, lastName, firstName])
+  @@map("patients")
+}
+
+model PatientTreatmentHistory {
+  id          String   @id @default(uuid())
+  patientId   String
+  title       String
+  status      String
+  treatmentAt DateTime
+  tooth       String?
+  notes       String?
+  totalCost   Float?
+  createdAt   DateTime @default(now())
+  updatedAt   DateTime @updatedAt
+
+  patient Patient @relation(fields: [patientId], references: [id], onDelete: Cascade)
+
+  @@index([patientId, treatmentAt])
+  @@map("patient_treatment_histories")
+}
+
 model Plan {
   id       String @id @default(uuid())
   name     String @unique // "Solo", "Small", "Medium", "Large", "Enterprise"