perf: reduce packaged locales and idle ADB polling

[man612]

Summary

Applies conservative, measurable Electron optimizations without pretending the framework itself can become tiny.

Package size

• keeps only the Electron locales Wirebound supports: en-US and id
• adds CI verification so extra Chromium locale packs cannot silently return
• reports unpacked Windows package size in the GitHub Actions step summary

Runtime overhead

• polls every 2s while a VPN client is connecting
• polls every 4s for active connected sessions
• backs off while disconnected
• backs off to 15s when Wirebound is idle in the tray
• keeps connected sessions responsive even when the main window is hidden

Tests

• adds unit coverage for the adaptive polling policy

This follows Electron's guidance to reduce unnecessary background work while hidden and electron-builder's supported locale-pruning configuration.