feat(04-03): Vendor, ExpenseCategory, Expense schema + category seeding + COA additions

- Add ExpenseStatus and ExpensePaymentMethod enums
- Add Vendor model (@@unique([tenantId, name]))
- Add ExpenseCategory model with accountCode linking to COA
- Add Expense model with approval workflow and JE reference
- Add User relations: createdExpenses, approvedExpenses
- Add COA accounts 5080 Fuel/Transportation, 5085 Rent Expense (31 total)
- Seed 9 default expense categories in createTenant transaction
- Add Vendor subject to CASL types, Expense/Vendor permissions for OFFICE_STAFF

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/accounting/chart-of-accounts.ts

@@ -276,6 +276,20 @@ export const ISP_CHART_OF_ACCOUNTS: COAAccountDefinition[] = [
     normalBalance: "DEBIT",
     parentCode: "5000",
   },
+  {
+    code: "5080",
+    name: "Fuel and Transportation",
+    accountType: "EXPENSE",
+    normalBalance: "DEBIT",
+    parentCode: "5000",
+  },
+  {
+    code: "5085",
+    name: "Rent Expense",
+    accountType: "EXPENSE",
+    normalBalance: "DEBIT",
+    parentCode: "5000",
+  },
   {
     code: "5090",
     name: "Other Expense",

src/lib/casl/permissions.ts

@@ -62,6 +62,10 @@ export function definePermissionsFor(
       can("update", "TechnicianProfile");
       // Inventory management
       can("manage", "Inventory");
+      // Expense management (record, list, view)
+      can("manage", "Expense");
+      // Vendor management (CRUD)
+      can("manage", "Vendor");
       // Job type rates (read-only for office staff — admin configures rates)
       can("read", "JobTypeRate");
       // View financial reports (read-only)

src/lib/casl/types.ts

@@ -20,6 +20,7 @@ export type AppSubjects =
   | "JobTypeRate"
   | "Inventory"
   | "Expense"
+  | "Vendor"
   | "Account"
   | "Report"
   | "all";

src/lib/tenant.ts

@@ -210,6 +210,22 @@ export async function createTenant(input: CreateTenantInput): Promise<CreateTena
     ];
     await tx.ticketCategory.createMany({ data: defaultCategories });
 
+    // Seed default ISP expense categories for this tenant.
+    // Each category maps to a COA expense account for automatic JE posting.
+    // System categories (isSystemCategory=true) cannot be deleted by admins.
+    const defaultExpenseCategories = [
+      { name: "Internet Bandwidth", accountCode: "5040", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Equipment & Supplies", accountCode: "5030", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Salary & Wages", accountCode: "5010", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Technician Compensation", accountCode: "5020", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Office Supplies", accountCode: "5050", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Utilities", accountCode: "5060", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Fuel & Transportation", accountCode: "5080", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Rent", accountCode: "5085", isSystemCategory: true, tenantId: tenant.id },
+      { name: "Other", accountCode: "5090", isSystemCategory: true, tenantId: tenant.id },
+    ];
+    await tx.expenseCategory.createMany({ data: defaultExpenseCategories });
+
     return { tenant, user };
   });