Implement SyncWarden v0.1.0

Full Syncthing tray wrapper with:
- System tray with 5 icon states (idle/syncing/paused/error/disconnected)
- Syncthing REST API client with auto-discovered API key
- Long-polling event listener for real-time status
- Transfer rate monitoring, folder tracking, recent files, conflict counting
- Full context menu with folders, recent files, settings toggles
- Embedded admin panel binary (webview, requires CGO)
- OS notifications via beeep (per-event configurable)
- Syncthing process management with auto-restart
- Cross-platform installer with autostart
- CI pipeline for Linux (.deb + .tar.gz) and Windows (.zip)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packaging/linux/postinstall.sh

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+#!/bin/sh
+echo "SyncWarden installed. It will start automatically on next login."
+echo "To start now: syncwarden &"

packaging/linux/preremove.sh

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+#!/bin/sh
+pkill -f syncwarden || true

packaging/linux/syncwarden.desktop

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+[Desktop Entry]
+Type=Application
+Name=SyncWarden
+Comment=System tray wrapper for Syncthing
+Exec=/usr/bin/syncwarden
+Terminal=false
+Categories=Network;FileTransfer;
+X-GNOME-Autostart-enabled=true