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>

package.json

@@ -10,11 +10,18 @@
     "db:init": "wrangler d1 execute telegram-summary-db --file=schema.sql",
     "db:init:local": "wrangler d1 execute telegram-summary-db --local --file=schema.sql",
     "tail": "wrangler tail",
-    "chat": "npx tsx scripts/chat.ts"
+    "chat": "npx tsx scripts/chat.ts",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage"
   },
   "devDependencies": {
+    "@cloudflare/vitest-pool-workers": "^0.1.0",
     "@cloudflare/workers-types": "^4.20241127.0",
+    "@vitest/coverage-v8": "^1.2.0",
+    "miniflare": "^3.20231030.0",
     "typescript": "^5.3.3",
+    "vitest": "^1.2.0",
     "wrangler": "^4.59.2"
   },
   "keywords": [