Add professor share calculation and financial reporting feature

Introduces per-class payout configuration (percentage or hourly rate,
plus an optional per-session expense allowance), pure calculation
utilities for professor payout/net profit/receivables, and a new
financial-reports API surface with per-class, per-session, and
date-range/monthly reports. Also adds full CRUD for institutional
expenses used in the range report, and wires up the new permissions
and roles. Fixes a pre-existing ReferenceError (missing
parseImportDate import) in paymentService that blocked creating
payments with dated transactions.

seed.js

@@ -57,7 +57,11 @@ const defaultRoles = [
       PERMISSIONS.CONTACT_INQUIRIES_READ,
       PERMISSIONS.CONTACT_INQUIRIES_UPDATE,
       PERMISSIONS.PENDING_STUDENTS_READ,
-      PERMISSIONS.PENDING_STUDENTS_UPDATE
+      PERMISSIONS.PENDING_STUDENTS_UPDATE,
+      PERMISSIONS.EXPENSES_CREATE,
+      PERMISSIONS.EXPENSES_READ,
+      PERMISSIONS.EXPENSES_UPDATE,
+      PERMISSIONS.FINANCIAL_REPORTS_READ
     ],
     isSystem: true
   },