Implement opal-task Phase 1: Database foundation

- Add SQLite database with schema for tasks, tags, and working_set
- Implement config management with Viper (opal.yml)
- Create Task struct with proper types (*time.Time, Priority int)
- Add database migration system
- Implement recurrence pattern parsing (1d, 1w, 1m, 1y)
- Setup project structure with cmd/ and internal/engine/
- Add dependencies: sqlite3, uuid, cobra, viper, color

opal-task/internal/engine/config.go

@@ -0,0 +1,123 @@
+package engine
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/viper"
+)
+
+type Config struct {
+	DefaultFilter string `mapstructure:"default_filter"`
+	DefaultSort   string `mapstructure:"default_sort"`
+	ColorOutput   bool   `mapstructure:"color_output"`
+}
+
+var globalConfig *Config
+
+// GetConfigDir returns the configuration directory path
+func GetConfigDir() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get home directory: %w", err)
+	}
+	return filepath.Join(home, ".config", "jade"), nil
+}
+
+// GetDBPath returns the path to the SQLite database
+func GetDBPath() (string, error) {
+	configDir, err := GetConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(configDir, "opal.db"), nil
+}
+
+// GetConfigPath returns the path to the config file
+func GetConfigPath() (string, error) {
+	configDir, err := GetConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(configDir, "opal.yml"), nil
+}
+
+// LoadConfig loads the configuration from file or creates default
+func LoadConfig() (*Config, error) {
+	if globalConfig != nil {
+		return globalConfig, nil
+	}
+
+	configDir, err := GetConfigDir()
+	if err != nil {
+		return nil, err
+	}
+
+	// Ensure config directory exists
+	if err := os.MkdirAll(configDir, 0755); err != nil {
+		return nil, fmt.Errorf("failed to create config directory: %w", err)
+	}
+
+	configPath, err := GetConfigPath()
+	if err != nil {
+		return nil, err
+	}
+
+	v := viper.New()
+	v.SetConfigFile(configPath)
+	v.SetConfigType("yaml")
+
+	// Set defaults
+	v.SetDefault("default_filter", "status:pending")
+	v.SetDefault("default_sort", "due,priority")
+	v.SetDefault("color_output", true)
+
+	// Try to read existing config
+	err = v.ReadInConfig()
+	if err != nil {
+		// Config doesn't exist, create it with defaults
+		// Write config with defaults (ignoring the error type check for now)
+		if err := v.WriteConfigAs(configPath); err != nil {
+			return nil, fmt.Errorf("failed to create config file: %w", err)
+		}
+		// Try reading again
+		if err := v.ReadInConfig(); err != nil {
+			return nil, fmt.Errorf("failed to read newly created config: %w", err)
+		}
+	}
+
+	cfg := &Config{}
+	if err := v.Unmarshal(cfg); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
+	}
+
+	globalConfig = cfg
+	return cfg, nil
+}
+
+// SaveConfig saves the configuration to file
+func SaveConfig(cfg *Config) error {
+	configPath, err := GetConfigPath()
+	if err != nil {
+		return err
+	}
+
+	v := viper.New()
+	v.SetConfigFile(configPath)
+	v.SetConfigType("yaml")
+
+	v.Set("default_filter", cfg.DefaultFilter)
+	v.Set("default_sort", cfg.DefaultSort)
+	v.Set("color_output", cfg.ColorOutput)
+
+	return v.WriteConfig()
+}
+
+// GetConfig returns the loaded config or loads it if not already loaded
+func GetConfig() (*Config, error) {
+	if globalConfig != nil {
+		return globalConfig, nil
+	}
+	return LoadConfig()
+}