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/resolver/resolver.go

@@ -0,0 +1,64 @@
+// Package resolver provides iterative DNS resolution from root nameservers.
+package resolver
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+
+	"go.uber.org/fx"
+
+	"sneak.berlin/go/dnswatcher/internal/logger"
+)
+
+// ErrNotImplemented indicates the resolver is not yet implemented.
+var ErrNotImplemented = errors.New("resolver not yet implemented")
+
+// Params contains dependencies for Resolver.
+type Params struct {
+	fx.In
+
+	Logger *logger.Logger
+}
+
+// Resolver performs iterative DNS resolution from root servers.
+type Resolver struct {
+	log *slog.Logger
+}
+
+// New creates a new Resolver instance.
+func New(
+	_ fx.Lifecycle,
+	params Params,
+) (*Resolver, error) {
+	return &Resolver{
+		log: params.Logger.Get(),
+	}, nil
+}
+
+// LookupNS performs iterative resolution to find authoritative
+// nameservers for the given domain.
+func (r *Resolver) LookupNS(
+	_ context.Context,
+	_ string,
+) ([]string, error) {
+	return nil, ErrNotImplemented
+}
+
+// LookupAllRecords performs iterative resolution to find all DNS
+// records for the given hostname.
+func (r *Resolver) LookupAllRecords(
+	_ context.Context,
+	_ string,
+) (map[string][]string, error) {
+	return nil, ErrNotImplemented
+}
+
+// ResolveIPAddresses resolves a hostname to all IPv4 and IPv6
+// addresses, following CNAME chains.
+func (r *Resolver) ResolveIPAddresses(
+	_ context.Context,
+	_ string,
+) ([]string, error) {
+	return nil, ErrNotImplemented
+}