ui: fix ETag truncation with MSVC compiler

[EZForever]

Overview

In the process of generating ETags for embedded web UI files, the uint64_t file hash is casted into a unsigned long value before being converted into a 64-bit hexadecimal string. MSVC compiler uses 32 bit long values, and thus will truncate the hash value. This don't really affect anything (aside for some ridiculous hypothetical load-balancing setup with servers running different OSes), but hey, why do a type cast when you can use the full value just like on Linux?

For consistency, type cast on the size_t value above is also removed. I don't really believe we will have 4GB+ of static files, though.

Additional information

Tested on Windows 11 with Visual Studio 2026.

Current master:

C:\Users\EZForever>curl -I http://127.0.0.1:9070/bundle.js
HTTP/1.1 200 OK
Server: llama.cpp
Access-Control-Allow-Origin:
ETag: "0x000000002639b40d"
Content-Type: application/javascript; charset=utf-8
Content-Length: 5285413
Accept-Ranges: bytes
Keep-Alive: timeout=5, max=100

This PR:

C:\Users\EZForever>curl -I http://127.0.0.1:9070/bundle.js
HTTP/1.1 200 OK
Server: llama.cpp
Access-Control-Allow-Origin:
ETag: "0xf0f916632639b40d"
Content-Type: application/javascript; charset=utf-8
Content-Length: 5285413
Accept-Ranges: bytes
Keep-Alive: timeout=5, max=100

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: NO

[allozaur]

Sth is causing ubuntu Server jobs to fail... not sure if this is caused by changes from this PR or sth else..?

@aldehir please take a look

[aldehir]

@allozaur seems unrelated to this PR, for example #23913 (comment) also fails. Probably needs to be bisected.