Enable strict TypeScript and reject non-null and definite-assignment assertions. Declare externally populated DTO fields, preserve runtime validation, and narrow values at their owners.
Verified: backend verify (257 tests), unchanged OpenAPI, and 21 SQLite/HTTP tests on retry. The initial SQLite run had two timeouts; baseline HEAD passed 21 tests as well.
Store exact RUB balances, atomic transfers, linked refunds and versioned edits independently of T-Bank. Add migration, HTTP and durability verification.
ksv741