feat: system service management (gyandoot service install|remove|status)

- Create systemd + launchd service templates in resources/
- Add gyandoot-core/src/service.rs module with full lifecycle
  - systemd: user service, daemon-reload, enable, start, stop, disable
  - launchd: macOS plist, load/unload, start/stop (launchctl)
- Add 'gyandoot service install|remove|status' CLI subcommand
- Update setup wizard: prompts 'Install system service? [y/N]'
- Update install.sh: prompts user for service install after binary
- Browser auto-starts at runtime (browser_manager), no separate service needed
- Camoufox installed via npm, auto-started by GyanDoot agent loop

resources/systemd/gyandoot.service

@@ -0,0 +1,31 @@
+[Unit]
+Description=GyanDoot v2.0 — AI Agent Platform
+Documentation=https://git.gyannetra.in/gnpl_admin/gyandoot-v2
+After=network.target network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=%USER%
+Group=%GROUP%
+ExecStart=%BINARY% serve --host 127.0.0.1 --port 8777
+Restart=on-failure
+RestartSec=5
+TimeoutStopSec=10
+KillMode=mixed
+StandardOutput=append:%HOME%/.gyandoot/service.log
+StandardError=append:%HOME%/.gyandoot/service.log
+
+# Environment
+Environment=GYANDOOT_CONFIG=%HOME%/.config/gyandoot/config.toml
+Environment=GYANDOOT_LOG=info
+
+# Security hardening
+NoNewPrivileges=true
+PrivateTmp=true
+ProtectHome=read-only
+ProtectSystem=strict
+ReadWritePaths=%HOME%/.gyandoot %HOME%/.config/gyandoot
+
+[Install]
+WantedBy=multi-user.target