feat: add Arch update helper and web UI

internal/config/config.go

@@ -0,0 +1,65 @@
+package config
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+)
+
+type Config struct {
+	CheckAUR              bool   `json:"check_aur"`
+	ReminderIntervalHours int    `json:"reminder_interval_hours"`
+	Terminal              string `json:"terminal"`
+}
+
+func Default() Config {
+	return Config{
+		CheckAUR:              true,
+		ReminderIntervalHours: 168,
+		Terminal:              "auto",
+	}
+}
+
+func Load(path string) (Config, error) {
+	cfg := Default()
+
+	data, err := os.ReadFile(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return cfg, nil
+	}
+	if err != nil {
+		return cfg, err
+	}
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return cfg, err
+	}
+
+	cfg = normalize(cfg)
+	return cfg, nil
+}
+
+func Save(path string, cfg Config) error {
+	cfg = normalize(cfg)
+
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+
+	data, err := json.MarshalIndent(cfg, "", "  ")
+	if err != nil {
+		return err
+	}
+	data = append(data, '\n')
+	return os.WriteFile(path, data, 0o644)
+}
+
+func normalize(cfg Config) Config {
+	if cfg.ReminderIntervalHours <= 0 {
+		cfg.ReminderIntervalHours = Default().ReminderIntervalHours
+	}
+	if cfg.Terminal == "" {
+		cfg.Terminal = Default().Terminal
+	}
+	return cfg
+}