fix: harden auth and investment synchronization

Resolve A01-A10 and C01-C07 from the backend audit.
Preserve auth failures, forced candle reconciliation and forecast freshness.
Validate MOEX responses and nested HTTP errors; remove unused legacy paths.

Verified: 209 unit tests, 262 SQLite e2e tests on Linux, OpenAPI and durability.
Record the remaining macOS native SQLite abort in the audit.

src/modules/investments/operations/infrastructure/brokerage-operation.mapper.spec.ts

@@ -4,6 +4,17 @@ import {
 } from './brokerage-operation.mapper';
 
 describe('mapBrokerageOperation', () => {
+  it('keeps subsecond timestamps at persisted millisecond precision and the standalone epoch default', () => {
+    expect(
+      mapBrokerageOperation({
+        date: { seconds: '1768000000', nanos: 600999999 },
+      }).occurredAt,
+    ).toBe('2026-01-09T23:06:40.600Z');
+    expect(mapBrokerageOperation({}).occurredAt).toBe(
+      '1970-01-01T00:00:00.000Z',
+    );
+  });
+
   it.each([
     ['OPERATION_TYPE_COUPON', 'income'],
     ['OPERATION_TYPE_DIVIDEND', 'income'],