Add UAC elevation support with manifest

- Added guruconnect.manifest requesting highestAvailable privileges
- Using winres to embed manifest in executable
- Added is_elevated() function to detect admin status
- Logs elevation status on startup
- Manifest includes Windows 7-11 compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

agent/Cargo.toml

@@ -79,6 +79,7 @@ windows-service = "0.7"
 
 [build-dependencies]
 prost-build = "0.13"
+winres = "0.1"
 
 [profile.release]
 lto = true