fix: resolve Docker file URL networking issue for plugins (#21334)

[krikera]

Fixes #21334

Problem

Using STORAGE_TYPE=local and FILES_URL=http://localhost no longer works in Docker environments. Plugin daemon cannot access files uploaded by users.

Solution

• Added INTERNAL_FILES_URL config for Docker network communication
• Plugin file access now uses internal Docker service URLs (e.g., http://api:5001)
• User downloads continue using external URLs (e.g., http://localhost:5001)
• Simple fallback: uses FILES_URL if INTERNAL_FILES_URL not set

Configuration

Add to Docker environment:

INTERNAL_FILES_URL=http://api:5001

Testing

• ✅ Plugin file access works in Docker
• ✅ User file downloads work from browser
• ✅ Backward compatible with existing setups

[Yeuoly]

I guess docker/*compose.yml need to be modified also.

stale

[gk0916]

Hello, I'm encountering an issue.
When set INTERNAL_FILES_URL=http://api:5001.
The URL of the output file of the tool node is prefixed with INTERNAL_FILES_URL. When the answer node references and outputs the file output by the tool node, the file URL displayed on the front end is also prefixed with INTERNAL_FILES_URL, which makes it impossible to preview and download the file on the front end.

The output of the answer node is as follows:
{
"answer": "1.wav",
"files": [
{
"dify_model_identity": "dify__file",
"id": null,
"tenant_id": "05f47de6-6d2a-4fb2-9c21-d57879a69f0a",
"type": "audio",
"transfer_method": "tool_file",
"remote_url": null,
"related_id": "c942b89f-5adb-4892-b685-da28ea9b3bc5",
"filename": "1.wav",
"extension": ".bin",
"mime_type": "audio/wav",
"size": 30064908,
"url": "http://api:5001/files/tools/c942b89f-5adb-4892-b685-da28ea9b3bc5.bin?timestamp=1753954013&nonce=a0b1a45fadfae82f95620094e0c9756d&sign=qYnbvkrgI_QA2o8fMRvIJ1JgJ9MUWW1RWC89MtlY0w8="
}
]
}