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

Filter non-RUB data at ingest and collapse per-currency collections
into a single RUB Money. Drop currency from TbankPortfolioValuePoint,
remove NON_RUB_ACTIVITY and the screener currency filter.

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

prisma/migrations/20261108000000_rub_only_value_points/migration.sql

@@ -0,0 +1,32 @@
+-- RedefineTables
+PRAGMA defer_foreign_keys=ON;
+PRAGMA foreign_keys=OFF;
+CREATE TABLE "new_TbankPortfolioValuePoint" (
+    "userId" TEXT NOT NULL,
+    "accountId" TEXT NOT NULL,
+    "attemptId" TEXT NOT NULL,
+    "value" TEXT NOT NULL,
+    "capturedAt" DATETIME NOT NULL,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    PRIMARY KEY ("userId", "accountId", "attemptId"),
+    CONSTRAINT "TbankPortfolioValuePoint_userId_accountId_fkey" FOREIGN KEY ("userId", "accountId") REFERENCES "TbankPortfolioValueHistory" ("userId", "accountId") ON DELETE CASCADE ON UPDATE RESTRICT
+);
+-- RUB-only: keep the RUB row per key; non-RUB rows are dropped.
+INSERT INTO "new_TbankPortfolioValuePoint" ("accountId", "attemptId", "capturedAt", "createdAt", "userId", "value")
+SELECT "accountId", "attemptId", "capturedAt", "createdAt", "userId", "value"
+FROM "TbankPortfolioValuePoint"
+WHERE "currency" = 'RUB';
+DROP TABLE "TbankPortfolioValuePoint";
+ALTER TABLE "new_TbankPortfolioValuePoint" RENAME TO "TbankPortfolioValuePoint";
+CREATE INDEX "TbankPortfolioValuePoint_userId_accountId_capturedAt_idx" ON "TbankPortfolioValuePoint"("userId", "accountId", "capturedAt");
+
+-- RUB-only: persisted JSON payloads written in the old multi-currency shape
+-- are stale. A missing snapshot/forecast is the app's normal "not synced yet"
+-- state: reads report availability 'missing' and the hourly walk rebuilds them
+-- on the next pass. Delete the stale rows instead of failing reads with 500.
+DELETE FROM "TbankPortfolio";
+DELETE FROM "TbankForecast";
+
+PRAGMA foreign_keys=ON;
+PRAGMA defer_foreign_keys=OFF;