Maps Trades (BUY/SELL) and CashTransactions (DIVIDEND, TAX, INTEREST, FEE,
DEPOSIT, WITHDRAWAL) from an IBKR Flex Activity Query to broker-sync
Activity objects. Adds canonical_symbol helper (LSE → .L suffix when
exchange=LSE* or currency=GBP). Exposes OpenPositions for the
reconciliation step that runs at the CLI layer.
Guards against wrong-account writes by checking
stmt.accountId == IBKR_ACCOUNT_ID_UPSTREAM before yielding any activities.
13 unit tests cover all the mappings + the mismatch guard.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
