Restrict renderer privileges

[enaboapps]

Closes #659

Summary

• register every Tauri application command through AppManifest and generate explicit command permissions
• split the main and modifier-overlay windows into separate least-privilege capabilities
• enforce a production CSP for local assets and Tauri IPC while leaving development CSP disabled
• add configuration tests for command registration, main access, overlay isolation, and CSP

Validation

• npm run lint
• npm test (74 frontend tests and 5 updater-feed tests)
• npm run build
• npm audit --audit-level=high
• cargo fmt, clippy with warnings denied, and tests for the app, updater verifier, and startup launcher
• cargo audit 0.22.2 for all three lockfiles
• 229 Rust unit tests and 7 configuration tests
• unsigned Windows UIAccess NSIS build and package verification