fix(backend): prevent query panic on short packets, optimize IP resolution, and stream checksum calculation

[JOsee321]

Summary of Changes

1. Fix Slice Out-of-Bounds Panic in UDP Query (query.rs):

   • Added a minimum length check (amt < 11) before slicing buffer headers. Prevents unexpected thread panic when receiving truncated or corrupted UDP packets.

2. Optimize IP Parsing & Eliminate Repeated Regex Compilation (query.rs):

   • Replaced on-the-fly Regex::new compilation on every query with native standard library addr.parse::<Ipv4Addr>() and socket_address.ip() matching.
   • Eliminates redundant CPU/heap overhead during high-frequency server polling.

3. Streamed MD5 Checksum Calculation (commands.rs):

   • Replaced f.read_to_end(&mut contents) with a 64KB chunked buffer stream feeding into md5::Context.
   • Prevents memory exhaustion / Out-Of-Memory (OOM) crashes on 32-bit Windows builds when calculating checksums for large archive/game files.

Testing

• Verified clean compilation and correct error handling on invalid/short buffers.
• Verified MD5 checksum output consistency with buffered streaming.