Data Statistics Tab Permission Update
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I have restricted access to the "Data Statistics" (数据统计) tab in the Admin Dashboard.

**Changes Made:**

1.  **Frontend (static/db_admin.html)**:
    -   Modified `setupTabsByRole`:
        -   Logic added to check if the current user is `admin` or `fssjsj`.
        -   If unauthorized, the "Data Statistics" tab button is hidden (`display: none`).
        -   If an unauthorized user attempts to access the tab via URL (`?tab=overview`), they are automatically redirected to the "Data Query" (`permits`) tab.
        -   Data loading for the overview tab is prevented for unauthorized users.
    -   Modified `switchTab`:
        -   Added a guard clause to prevent authorized users from programmatically switching to the overview tab.

**Verification:**
-   **Authorized Users**: `admin` and `fssjsj` can see and access the "Data Statistics" tab.
-   **Unauthorized Users**: All other users will not see the tab and will default to the "Data Query" tab.
