Accessing Uploaded Attachments and Images Return HTTP 302 with Location /403

## Describe the bug

Add images and attachment to a post successfully, no error shows up, and then reopen the post, but image isn't displayed and attachement can't be downloaded.

I inspect the network activities. Refreshing the post with the image sends HTTP GET, but receives HTTP 302 response with location /403.

Clicking the attachment sends the HTTP GET, but receives HTTP 302 response with location /403.

### To Reproduce

Steps to reproduce the behavior:

1. Unpack binary distribution from github, to directory ~/apache-answer-1.4.5-bin-linux-amd64, where there is the executable.
2. Follow the guide on the official site.
3. Run the command and set up database, email and admin.

`ubuntu@VM-0-8-ubuntu:~/apache-answer-1.4.5-bin-linux-amd64$ sudo ./answer init -C ./answer-data/`

4. Run the command to bring up the forum.

`ubuntu@VM-0-8-ubuntu:~/apache-answer-1.4.5-bin-linux-amd64$ sudo nohup ./answer run -C ./answer-data/`

5. Login, create a new question, post an image or upload an attachment.
6. Go back to landing page and reopen the previous post to examine the image and attachement, can't be shown or downloaded.
7. Inspect the network activities with dev tool and locate the URL:

`http://plusai.site/uploads/files/post/5smfTQVm1EU/test.pdf`
`http://plusai.site/uploads/post/5smt4sbUZA9.png`

8. On server, navigate to the data directory, which is

`~/apache-answer-1.4.5-bin-linux-amd64/answer-data`

The path to previous uploaded files are

`~/apache-answer-1.4.5-bin-linux-amd64/answer-data/uploads/files/post/5smfTQVm1EU.pdf`
`~/apache-answer-1.4.5-bin-linux-amd64/answer-data/uploads/post/5smt4sbUZA9.png`

9. confi.yaml after initialization is like
`
ui:
base_url: ""
api_base_url: ""
`

There is **_no public_url arttribute_**.

### Expected behavior

Image is displayed, and attachment can be downloaded by clicking the link.

### Screenshots

No screenshot.

### Platform

- Device: Server
- OS: Ubuntu 2024.5
- Browser and version: Edge Lastest
- Version: 1.4.5

Riproduci il problema con il binario 1.4.5 usando `answer init -C ./answer-data/` e `answer run -C ./answer-data/`, quindi esamina gli URL di upload, i reindirizzamenti, `confi.yaml` e i file sotto `answer-data/uploads/`. Traccia il motivo per cui le richieste di immagini e allegati vengono reindirizzate a `/403`; il lavoro è completato quando le immagini vengono visualizzate e gli allegati vengono scaricati correttamente.

Scritto dal modello di indicizzazione a partire dal testo della issue.