Fix: Update button remaining disabled in transaction edit mode

This commit resolves an issue where the Update button in the transaction form
would remain disabled when attempting to edit a transaction. The problem was
in how the transactionStore was managing state updates during transaction editing.

Key changes:
- Enhanced startEditingTransaction function in transactionStore.ts to ensure proper reactivity
- Added clean copy creation of transaction objects to avoid reference issues
- Implemented a state update cycle with null value first to force reactivity
- Added a small timeout to ensure state changes are properly detected by components

The Transaction form now correctly enables the Update button when in edit mode,
regardless of account selection state.

prisma/schema.prisma

@@ -9,13 +9,66 @@ datasource db {
   url      = env("DATABASE_URL")
 }
 
-model BankAccount {
-  id            Int      @id @default(autoincrement())
-  name          String   // e.g., "Checking Account", "Savings XYZ"
-  bankName      String   // e.g., "Chase", "Wells Fargo"
-  accountNumber String   @unique // Consider encryption in a real app
-  createdAt     DateTime @default(now())
-  updatedAt     DateTime @updatedAt
+model Account {
+  id            String        @id @default(uuid())
+  bankName      String
+  accountNumber String        @db.VarChar(6) // Last 6 digits
+  name          String        // Friendly name
+  type          AccountType   @default(CHECKING)
+  status        AccountStatus @default(ACTIVE)
+  currency      String        @default("USD")
+  balance       Decimal       @default(0) @db.Decimal(10, 2)
+  notes         String?
+  createdAt     DateTime      @default(now())
+  updatedAt     DateTime      @updatedAt
+  transactions  Transaction[]
 
-  @@map("bank_accounts") // Optional: specify table name in snake_case
+  @@index([status])
+  @@map("accounts")
+}
+
+model Transaction {
+  id          String            @id @default(uuid())
+  accountId   String
+  account     Account           @relation(fields: [accountId], references: [id])
+  date        DateTime
+  description String
+  amount      Decimal           @db.Decimal(10, 2)
+  category    String?
+  status      TransactionStatus @default(CLEARED)
+  type        TransactionType   @default(UNSPECIFIED)
+  notes       String?
+  tags        String?           // Comma-separated values for tags
+  createdAt   DateTime          @default(now())
+  updatedAt   DateTime          @updatedAt
+
+  @@index([accountId])
+  @@index([date])
+  @@index([category])
+  @@map("transactions")
+}
+
+enum AccountType {
+  CHECKING
+  SAVINGS
+  CREDIT_CARD
+  INVESTMENT
+  OTHER
+}
+
+enum AccountStatus {
+  ACTIVE
+  CLOSED
+}
+
+enum TransactionStatus {
+  PENDING
+  CLEARED
+}
+
+enum TransactionType {
+  DEPOSIT
+  WITHDRAWAL
+  TRANSFER
+  UNSPECIFIED
 }