Adds expense tracking module

Adds a new module for tracking user expenses.

The module includes:
- Configuration settings for the LNbits API endpoint and timeouts.
- An ExpensesAPI service for fetching accounts and submitting expense entries.
- A UI component for adding expenses, including account selection and form input.
- Dependency injection for the ExpensesAPI service.

This allows users to submit expense entries with account selection and reference data, which will be linked to their wallet.

src/modules/expenses/index.ts

@@ -0,0 +1,58 @@
+/**
+ * Expenses Module
+ *
+ * Provides expense tracking and submission functionality
+ * integrated with castle LNbits extension.
+ */
+
+import type { App } from 'vue'
+import { markRaw } from 'vue'
+import type { ModulePlugin } from '@/core/types'
+import { container, SERVICE_TOKENS } from '@/core/di-container'
+import { ExpensesAPI } from './services/ExpensesAPI'
+import AddExpense from './components/AddExpense.vue'
+
+export const expensesModule: ModulePlugin = {
+  name: 'expenses',
+  version: '1.0.0',
+  dependencies: ['base'],
+
+  quickActions: [
+    {
+      id: 'add-expense',
+      label: 'Expense',
+      icon: 'DollarSign',
+      component: markRaw(AddExpense),
+      category: 'finance',
+      order: 10,
+      requiresAuth: true
+    }
+  ],
+
+  async install(app: App) {
+    console.log('[Expenses Module] Installing...')
+
+    // 1. Create and register service
+    const expensesAPI = new ExpensesAPI()
+    container.provide(SERVICE_TOKENS.EXPENSES_API, expensesAPI)
+
+    // 2. Initialize service (wait for dependencies)
+    await expensesAPI.initialize({
+      waitForDependencies: true,
+      maxRetries: 3,
+      retryDelay: 1000
+    })
+
+    console.log('[Expenses Module] ExpensesAPI initialized')
+
+    // 3. Register components globally (optional, for use outside quick actions)
+    app.component('AddExpense', AddExpense)
+
+    console.log('[Expenses Module] Installed successfully')
+  }
+}
+
+export default expensesModule
+
+// Export types for use in other modules
+export type { Account, AccountNode, ExpenseEntry, ExpenseEntryRequest } from './types'