[High] Memory Leak in metamask-extension

## Bug Report

**Type**: Memory Leak
**Severity**: High
**File**: src/core/metamask-extension.ts:234

### Description
发现数据库连接在异常情况下未正确关闭，导致内存泄漏。

### Impact
- 长期运行内存占用持续增长
- 可能导致服务崩溃

### Proposed Fix
使用try-finally确保资源释放。

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Automated Bug Report - 2026-02-05

Start by reading src/core/metamask-extension.ts around line 234 and trace the database connection through its exceptional path. Confirm which resource remains open when an exception occurs, then verify that the connection is released and long-running memory usage no longer grows. No test file is named in the issue, so identify the relevant existing test or validation command from the repository.

Written by the indexing model from the issue text.