refactor!: support RUB only (WealthLedger/main#55) (#204)

BREAKING CHANGE: per-currency API fields replaced with single RUB Money.

prisma/schema.prisma

@@ -101,18 +101,17 @@ model TbankPortfolioValueHistory {
   @@id([userId, accountId])
 }
 
-// One row per currency of a fully valued successful portfolio attempt.
+// One row per fully valued successful portfolio attempt (RUB only).
 model TbankPortfolioValuePoint {
   userId String
   accountId String
   attemptId String
-  currency String
   value String
   capturedAt DateTime
   createdAt DateTime @default(now())
   history TbankPortfolioValueHistory @relation(fields: [userId, accountId], references: [userId, accountId], onDelete: Cascade, onUpdate: Restrict)
 
-  @@id([userId, accountId, attemptId, currency])
+  @@id([userId, accountId, attemptId])
   @@index([userId, accountId, capturedAt])
 }