feat: implement SSH honeypot server with auth and config

Add core SSH server with password authentication, per-IP failure
tracking, credential memory with TTL, and static credential support.
Includes TOML config loading with validation, Ed25519 host key
auto-generation, and a Nix package output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/oubliette/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"log/slog"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"git.t-juice.club/torjus/oubliette/internal/config"
+	"git.t-juice.club/torjus/oubliette/internal/server"
+)
+
+func main() {
+	configPath := flag.String("config", "oubliette.toml", "path to config file")
+	flag.Parse()
+
+	cfg, err := config.Load(*configPath)
+	if err != nil {
+		slog.Error("failed to load config", "err", err)
+		os.Exit(1)
+	}
+
+	level := new(slog.LevelVar)
+	switch cfg.LogLevel {
+	case "debug":
+		level.Set(slog.LevelDebug)
+	case "warn":
+		level.Set(slog.LevelWarn)
+	case "error":
+		level.Set(slog.LevelError)
+	default:
+		level.Set(slog.LevelInfo)
+	}
+
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: level}))
+	slog.SetDefault(logger)
+
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer cancel()
+
+	srv, err := server.New(*cfg, logger)
+	if err != nil {
+		logger.Error("failed to create server", "err", err)
+		os.Exit(1)
+	}
+
+	if err := srv.ListenAndServe(ctx); err != nil {
+		logger.Error("server error", "err", err)
+		os.Exit(1)
+	}
+
+	logger.Info("server stopped")
+}