Enable chunk based OTA updates

[MattCatz]

Pull in the Go project Desync. This allows us to split release files into chunks. Then OTA upgrades only need to get the new chunks between release. This saves a bit of time on network transfers depending on network conditions and starting version.

The desync binary is on the large side but is a statically linked executable. (no need to worry about compiling and linking dependencies).

Chunking enables upgrades from any version without requiring per-version deltas. A traditional delta system would need to generate and store a delta for every possible source/target pair; with chunking, unchanged data is reused regardless of the starting version.

This change-set does make OnionOS hold on to the old zip files. This is needed to seed the OTA download and consumes an extra 415 MB on the SD card depending on the release.

A few rough edges with this PR:

• go needs to be added to the toolchain docker image. Right now building desync requires the host machine to have go installed.
• No idea where to store chunks. The content store is all static. gh-pages could store a few releases worth of chunks. Cloudflares R2 free tier is another candidate.

I ported my changes back to some older releases to compare overlap. Below shows the number of unique chunks between each release.

# comm -23 ./Onion-v4.3.1.txt ./Onion-v4.3.1-1.txt | wc -l
268
# comm -23 ./Onion-v4.3.1.txt ./Onion-v4.4.0-beta-20260120.txt | wc -l
167
# comm -23 ./Onion-v4.3.1-1.txt ./Onion-v4.4.0-beta-20260120.txt | wc -l
12

I probably should have purposed this on the discord first but it ended up being a much smaller initial PR than I though it was going to be. Let me know what needs rework.