Add bulk actions, multi-currency, expenses, templates, and reports

Schema (migration 0001):
- clients: add currency column (default USD)
- invoices: add currency column (default USD)
- New expenses table: amount, currency, category, billable, reimbursable,
  client/invoice/business relations, notes
- New invoice_templates table: name, type (notes|terms), content, isDefault

API:
- invoices: add bulkUpdateStatus and bulkDelete procedures (ownership-safe)
- invoices: currency field threaded through create/update schemas
- clients: currency field added to create/update schemas
- New expenses router: full CRUD with authorization
- New invoiceTemplates router: full CRUD, isDefault management per type
- Root router: wire in expenses and invoiceTemplates

Currency (src/lib/currency.ts):
- Shared formatCurrency(amount, currency) utility replacing hardcoded USD
- SUPPORTED_CURRENCIES list (17 currencies)
- Invoice form: currency selector in Config card, auto-fills from client
- Client form: currency selector in Billing Information card

Bulk actions (invoices list):
- Checkbox column with select-all support
- Selection toolbar: Mark as Sent/Paid/Draft dropdown, Delete (N) button
- DataTable: new selectionActions prop renders toolbar when rows selected

Notes templates:
- Invoice form: Notes card with textarea in Details tab
- Template dropdown button appears when templates exist
- /dashboard/invoices/templates: full CRUD page for notes and terms templates

New pages:
- /dashboard/expenses: expense list with summary cards, add/edit dialog
- /dashboard/reports: KPI cards, 12-month revenue area chart, top clients
  bar chart, status breakdown, recent activity
- Navigation: Expenses and Reports added to Main section

https://claude.ai/code/session_012sqEgNQpx676isepeoX4Mi

src/server/api/root.ts

@@ -4,6 +4,8 @@ import { invoicesRouter } from "~/server/api/routers/invoices";
 import { settingsRouter } from "~/server/api/routers/settings";
 import { emailRouter } from "~/server/api/routers/email";
 import { dashboardRouter } from "~/server/api/routers/dashboard";
+import { expensesRouter } from "~/server/api/routers/expenses";
+import { invoiceTemplatesRouter } from "~/server/api/routers/invoiceTemplates";
 import { createCallerFactory, createTRPCRouter } from "~/server/api/trpc";
 
 /**
@@ -18,6 +20,8 @@ export const appRouter = createTRPCRouter({
   settings: settingsRouter,
   email: emailRouter,
   dashboard: dashboardRouter,
+  expenses: expensesRouter,
+  invoiceTemplates: invoiceTemplatesRouter,
 });
 
 // export type definition of API