[codex] Replace Prism Forge flow with native installers

[ExtremestoneGG]

What changed

• Replaced Prism metadata and ForgeWrapper usage with a VEX-native Forge and NeoForge installation flow.
• Reads compatible versions directly from the official Forge and NeoForge Maven catalogs.
• Downloads and runs the official installer silently after preparing the launcher environment it requires.
• Validates the exact generated loader profile before creating or launching an instance.
• Reads the required Java version from Mojang version metadata.
• Updated the instance editor copy and bumped VEX to 0.7.0.

Why

Forge instance creation was unreliable because the previous metadata-based implementation did not fully match the official installer behavior. The official installers require a launcher profile file in the target directory; VEX now prepares that requirement itself and cleans up its temporary file afterward.

Impact

Forge and NeoForge instances can be created without depending on Prism Launcher metadata or ForgeWrapper. The same flow is suitable for Windows and Linux.

Validation

• Installed Forge 1.21.1 / 52.1.14 successfully in an isolated directory.
• Installed NeoForge 1.21.1 / 21.1.233 successfully in an isolated directory.
• cargo check
• npm run build
• Built the Windows NSIS installer and self-contained portable executable.
• Portable executable startup smoke test passed.