feat: complete SyncServer implementation

Full-stack Go monolith with embedded React frontend for orchestrating
rsync-over-SSH file synchronization with Wake-on-LAN support.

Features:
- JWT auth (HS256) with bcrypt password hashing
- CRUD for machines (with WoL config) and sync_pairs
- Ed25519 SSH key generation and known_hosts management
- WoL magic packet sender + TCP-connect waiter with backoff
- Sync engine: rsync subprocess, per-pair job queue, progress parsing
- Homebrew cron parser for scheduled syncs
- SSE stream for live job status (queued/waking_up/running/success/failed)
- React+TS+Vite+Tailwind SPA embedded via embed.FS
- Debian packaging with systemd unit, postinst/prerm/postrm

Tech stack:
- Go 1.22+ (CGO_ENABLED=0, pure SQLite via modernc.org/sqlite)
- chi router for HTTP API
- TypeScript + React 18 + Tailwind CSS frontend
- Cross-compiled to Linux amd64 for Proxmox LXC deployment

Tests: wol (MAC parsing, magic packet), syncengine/queue, scheduler/cron

packaging/debian/DEBIAN/conffiles

@@ -0,0 +1 @@
+/etc/syncserver/config.yaml

packaging/debian/DEBIAN/control

@@ -0,0 +1,12 @@
+Package: syncserver
+Version: 1a66ac5
+Architecture: amd64
+Section: net
+Priority: optional
+Depends: rsync, openssh-client, ca-certificates
+Maintainer: SyncServer Team <syncserver@example.com>
+Description: Self-hosted file sync orchestrator with Wake-on-LAN and web UI
+ SyncServer is a Go-based server that provides a web interface to manage
+ and execute file synchronizations between multiple machines using rsync
+ over SSH, with optional Wake-on-LAN support to power on remote machines
+ before syncing.

packaging/debian/DEBIAN/postinst

@@ -0,0 +1,47 @@
+#!/bin/bash
+set -e
+
+case "$1" in
+    configure)
+        if ! id syncserver > /dev/null 2>&1; then
+            useradd --system --no-create-home --shell /usr/sbin/nologin syncserver || true
+        fi
+
+        install -d -o syncserver -g syncserver -m 0750 /var/lib/syncserver/data || true
+        install -d -o syncserver -g syncserver -m 0750 /var/lib/syncserver/ssh || true
+        install -d -o syncserver -g syncserver -m 0750 /var/lib/syncserver/logs || true
+        install -d -o root -g root -m 0755 /etc/syncserver || true
+
+        if [ ! -f /etc/syncserver/config.yaml ]; then
+            cat > /etc/syncserver/config.yaml << 'EOF'
+# SyncServer configuration
+# Copy this file and edit as needed.
+# Environment variables SYNCSERVER_* take precedence over this file.
+
+data_dir: /var/lib/syncserver
+addr: :8080
+
+auth:
+  jwt_secret: ""  # Leave empty to generate a random one on startup
+  jwt_expiry_hours: 24
+
+scheduler:
+  timezone: UTC
+EOF
+            chown root:root /etc/syncserver/config.yaml
+            chmod 0644 /etc/syncserver/config.yaml
+        fi
+
+        if command -v systemctl > /dev/null 2>&1; then
+            systemctl daemon-reload 2>/dev/null || true
+            systemctl enable syncserver.service 2>/dev/null || true
+            systemctl start syncserver.service 2>/dev/null || true
+        fi
+        ;;
+
+    abort-upgrade|abort-remove|abort-configure)
+        exit 0
+        ;;
+esac
+
+exit 0

packaging/debian/DEBIAN/postrm

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+
+case "$1" in
+    purge|remove)
+        if [ "$1" = "purge" ]; then
+            rm -rf /var/lib/syncserver || true
+        fi
+        ;;
+    upgrade)
+        ;;
+    failed-upgrade)
+        ;;
+    abort-install|abort-upgrade)
+        ;;
+    *)
+        exit 0
+        ;;
+esac
+
+exit 0

packaging/debian/DEBIAN/prerm

@@ -0,0 +1,20 @@
+#!/bin/bash
+set -e
+
+case "$1" in
+    remove|purge|deconfigure)
+        if command -v systemctl > /dev/null 2>&1; then
+            systemctl stop syncserver.service 2>/dev/null || true
+            systemctl disable syncserver.service 2>/dev/null || true
+        fi
+        ;;
+    upgrade)
+        ;;
+    failed-upgrade)
+        ;;
+    *)
+        exit 0
+        ;;
+esac
+
+exit 0

packaging/debian/lib/systemd/system/syncserver.service

@@ -0,0 +1,27 @@
+[Unit]
+Description=SyncServer - File sync orchestrator with Wake-on-LAN and web UI
+Documentation=https://github.com/syncserver/syncserver
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=syncserver
+Group=syncserver
+ExecStart=/usr/bin/syncserver --config /etc/syncserver/config.yaml --data-dir /var/lib/syncserver
+Restart=on-failure
+RestartSec=5
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=syncserver
+
+# Hardening
+NoNewPrivileges=true
+PrivateTmp=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/var/lib/syncserver /run
+UMask=0077
+
+[Install]
+WantedBy=multi-user.target