refactor: improve type safety and code quality for 9.0 score

Type Safety Improvements:
- Add isErrorResult() type guard for API responses (domain-tool.ts)
- Replace `any` with `unknown` in executeTool args (tools/index.ts)
- Add JSON.parse error handling in function calling (openai-service.ts)
- Fix nullable price handling with nullish coalescing
- Add array type guard for nameservers validation

Code Quality Improvements:
- Extract convertNamecheapDate() to eliminate duplicate functions
- Move hardcoded bank account info to environment variables
- Add JSDoc documentation to executeDepositFunction
- Fix unused variables in optimistic-lock.ts
- Handle Error.captureStackTrace for Workers environment

All TypeScript strict mode checks now pass.

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

src/tools/index.ts

@@ -117,7 +117,7 @@ export function selectToolsForMessage(message: string): typeof tools {
 // Tool execution dispatcher with validation
 export async function executeTool(
   name: string,
-  args: Record<string, any>,
+  args: Record<string, unknown>,
   env?: Env,
   telegramUserId?: string,
   db?: D1Database