feat(REQ-005): implement TrEx Basic V1 API contract with auth, assets, ledger, and user endpoints

- Add V1 API routes for assets, ledger, and user info with complete CRUD operations
- Implement authentication scopes and request validation via auth_routes.py
- Extend schemas with V1-specific models for accounts, holdings, and positions
- Add database queries and aggregations for P&L, performance, and account data
- Include comprehensive test coverage for all V1 endpoints and integration flows
- Update batch and release documentation with implementation and verification evidence
- Sync project structure and runtime flows per V1 API contract requirements

Closes implementation phase of BAT-001 (TrEx Basic V1 API Contract)

app/main.py

@@ -53,6 +53,8 @@ def create_app(
     @asynccontextmanager
     async def lifespan(_: FastAPI):
         _bootstrap_initial_user(settings, repository_factory)
+        if settings.db_enabled:
+            settings.require_credential_encryption_key()
         yield
 
     app = FastAPI(