Refactor invoice data table and templates page for improved readability and functionality

- Cleaned up imports and formatted code for better readability in invoices-data-table.tsx.
- Enhanced invoice interface definitions for clarity.
- Improved toast messages for bulk delete and update actions.
- Refactored date formatting and status type retrieval for better readability.
- Simplified template management in templates page, extracting TemplateList component.
- Added registration toggle based on environment variable DISABLE_SIGNUPS.
- Updated navbar to conditionally render registration link based on allowRegistration prop.
- Enhanced error handling and validation in expenses and settings routers.
- Improved PDF export footer handling.
- Updated TRPC react integration for cleaner type imports.

src/lib/auth.ts

@@ -10,6 +10,7 @@ const authentikEnabled = Boolean(
     process.env.AUTHENTIK_CLIENT_ID &&
     process.env.AUTHENTIK_CLIENT_SECRET,
 );
+const signupsDisabled = process.env.DISABLE_SIGNUPS === "true";
 
 export const auth = betterAuth({
   database: drizzleAdapter(db, {
@@ -34,6 +35,7 @@ export const auth = betterAuth({
   }),
   emailAndPassword: {
     enabled: true,
+    disableSignUp: signupsDisabled,
     password: {
       hash: async (password) => {
         const bcrypt = await import("bcryptjs");