Initial scaffold with per-nameserver DNS monitoring model

Full project structure following upaas conventions: uber/fx DI, go-chi
routing, slog logging, Viper config. State persisted as JSON file with
per-nameserver record tracking for inconsistency detection. Stub
implementations for resolver, portcheck, tlscheck, and watcher.

internal/watcher/watcher.go

@@ -0,0 +1,94 @@
+// Package watcher provides the main monitoring orchestrator and scheduler.
+package watcher
+
+import (
+	"context"
+	"log/slog"
+
+	"go.uber.org/fx"
+
+	"sneak.berlin/go/dnswatcher/internal/config"
+	"sneak.berlin/go/dnswatcher/internal/logger"
+	"sneak.berlin/go/dnswatcher/internal/notify"
+	"sneak.berlin/go/dnswatcher/internal/portcheck"
+	"sneak.berlin/go/dnswatcher/internal/resolver"
+	"sneak.berlin/go/dnswatcher/internal/state"
+	"sneak.berlin/go/dnswatcher/internal/tlscheck"
+)
+
+// Params contains dependencies for Watcher.
+type Params struct {
+	fx.In
+
+	Logger    *logger.Logger
+	Config    *config.Config
+	State     *state.State
+	Resolver  *resolver.Resolver
+	PortCheck *portcheck.Checker
+	TLSCheck  *tlscheck.Checker
+	Notify    *notify.Service
+}
+
+// Watcher orchestrates all monitoring checks on a schedule.
+type Watcher struct {
+	log       *slog.Logger
+	config    *config.Config
+	state     *state.State
+	resolver  *resolver.Resolver
+	portCheck *portcheck.Checker
+	tlsCheck  *tlscheck.Checker
+	notify    *notify.Service
+	cancel    context.CancelFunc
+}
+
+// New creates a new Watcher instance.
+func New(
+	lifecycle fx.Lifecycle,
+	params Params,
+) (*Watcher, error) {
+	watcher := &Watcher{
+		log:       params.Logger.Get(),
+		config:    params.Config,
+		state:     params.State,
+		resolver:  params.Resolver,
+		portCheck: params.PortCheck,
+		tlsCheck:  params.TLSCheck,
+		notify:    params.Notify,
+	}
+
+	lifecycle.Append(fx.Hook{
+		OnStart: func(startCtx context.Context) error {
+			ctx, cancel := context.WithCancel(startCtx)
+			watcher.cancel = cancel
+
+			go watcher.Run(ctx)
+
+			return nil
+		},
+		OnStop: func(_ context.Context) error {
+			if watcher.cancel != nil {
+				watcher.cancel()
+			}
+
+			return nil
+		},
+	})
+
+	return watcher, nil
+}
+
+// Run starts the monitoring loop.
+func (w *Watcher) Run(ctx context.Context) {
+	w.log.Info(
+		"watcher starting",
+		"domains", len(w.config.Domains),
+		"hostnames", len(w.config.Hostnames),
+		"dnsInterval", w.config.DNSInterval,
+		"tlsInterval", w.config.TLSInterval,
+	)
+
+	// Stub: wait for context cancellation.
+	// Implementation will add initial check + periodic scheduling.
+	<-ctx.Done()
+	w.log.Info("watcher stopped")
+}