feat: config generator module — auto-generate generalupdate.manifest.json

[JusterZhu]

Problem

New GeneralUpdate users face "configuration hell" — they must manually write generalupdate.manifest.json and Configinfo with correct field names, semver version format, and cross-machine compatible paths. Mistakes lead to cryptic runtime errors.

Solution

Add a "Config Generator" page to GeneralUpdate.Tools that auto-analyzes .csproj files and generates the correct generalupdate.manifest.json with a simple 3-step flow: Select → Review → Generate.

Implementation

See PR: #73