Add Velocity egg with Java 25 support

[iamthealfaandtheomega]

Adds a game egg for Velocity (Minecraft proxy) that did not exist in the panel's egg collection.

Highlights:

• Runs on Java 25 and Java 21 images (JDK 25 is already in the other Minecraft eggs)
• Installs the latest stable release build via the Fill v3 API, skipping snapshot/experimental trains
• Verifies the jar's SHA-256 against the value published by Fill before promoting it into place; on mismatch the install fails cleanly and no partial jar is left behind
• Uses Wings' file parser to rewrite the proxy bind address (TOML parsing is not supported by Wings and would be a no-op)
• Fails with a clear message when the API is unreachable

Tested locally: successful install (jar checksum verified), tampered download (clean abort), snapshot-only feed (clean abort), API outage (clean error), and config rewrite applied at runtime.

[SerenModz21]

It's worth noting that a lot of eggs are available at https://eggs.pterodactyl.io/, including Velocity.

• https://eggs.pterodactyl.io/egg/games-velocity/
• Source: https://github.com/pterodactyl/game-eggs/blob/main/minecraft/proxy/java/velocity/egg-velocity.json
• Java 25 PR: Add Java 25 docker image to egg-velocity.json game-eggs#602

[iamthealfaandtheomega]

Java 25 is not there.