feat: add optimistic locking and improve type safety

- Implement optimistic locking for deposit balance updates
  - Prevent race conditions in concurrent deposit requests
  - Add automatic retry with exponential backoff (max 3 attempts)
  - Add version column to user_deposits table

- Improve type safety across codebase
  - Add explicit types for Namecheap API responses
  - Add typed function arguments (ManageDepositArgs, etc.)
  - Remove `any` types from deposit-agent and tool files

- Add reconciliation job for balance integrity verification
  - Compare user_deposits.balance vs SUM(confirmed transactions)
  - Alert admin on discrepancy detection

- Set up test environment with Vitest + Miniflare
  - Add 50+ test cases for deposit system
  - Add helper functions for test data creation

- Update documentation
  - Add migration guide for version columns
  - Document optimistic locking patterns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

vitest.config.ts

@@ -0,0 +1,35 @@
+import { defineConfig } from 'vitest/config';
+import path from 'path';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'miniflare',
+    environmentOptions: {
+      bindings: {
+        BOT_TOKEN: 'test-bot-token',
+        WEBHOOK_SECRET: 'test-webhook-secret',
+        OPENAI_API_KEY: 'test-openai-key',
+        DEPOSIT_ADMIN_ID: '999999999',
+      },
+      kvNamespaces: ['RATE_LIMIT_KV'],
+      d1Databases: ['DB'],
+    },
+    setupFiles: ['./tests/setup.ts'],
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'json', 'html'],
+      exclude: [
+        'node_modules/',
+        'tests/',
+        '**/*.test.ts',
+        '**/__test__/',
+      ],
+    },
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+    },
+  },
+});