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

Makefile

@@ -0,0 +1,36 @@
+.PHONY: build dev clean deb run test lint
+
+VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo dev)
+GOARCH := amd64
+
+build:
+	GOARCH=$(GOARCH) ./scripts/build.sh
+
+deb:
+	./scripts/package-deb.sh
+
+clean:
+	rm -rf dist/
+	rm -rf internal/webui/dist/
+	go clean
+
+run: build
+	./syncserver --data-dir ./data --addr :8080
+
+dev:
+	cd web && npm run dev &
+
+test:
+	go test ./...
+
+lint:
+	go vet ./...
+
+fmt:
+	go fmt ./...
+
+# Build for local macOS (not for production)
+build-local:
+	rm -rf web/dist && cd web && npm run build && cd ..
+	cp -R web/dist internal/webui/dist/
+	go build -ldflags="-X main.version=$(VERSION)" -o syncserver ./cmd/server