fix: security hardening, tests, docs for Electron desktop & memory optimization
## Security Fixes
- Sanitize OMNIROUTE_MEMORY_MB with parseInt + range validation (64-16384)
to prevent command injection via spawn() args
- Validate URL protocol in shell.openExternal (http/https only)
to prevent RCE in Electron renderer compromise
- Bump default memory from 256MB to 512MB
## Electron package-lock.json
- Added to .gitignore (5278 lines removed from tracking)
## Test Suite (64 tests, 9 suites)
- electron-main.test.mjs: URL validation, IPC channels, window handler
- electron-preload.test.mjs: channel whitelist, API surface, open-external
- cli-memory.test.mjs: injection prevention, boundary values, .env parsing
## Documentation
- Desktop App section added to all 30 READMEs (9 fully translated)
- USER_GUIDE.md updated with 512MB default
- .env.example reflects new defaults
diegosouzapw
d3ace8d611