Major refactoring: UUID-based storage, streaming architecture, and CLI improvements

This commit represents a significant architectural overhaul of vaultik:

Database Schema Changes:
- Switch files table to use UUID primary keys instead of path-based keys
- Add UUID primary keys to blobs table for immediate chunk association
- Update all foreign key relationships to use UUIDs
- Add comprehensive schema documentation in DATAMODEL.md
- Add SQLite busy timeout handling for concurrent operations

Streaming and Performance Improvements:
- Implement true streaming blob packing without intermediate storage
- Add streaming chunk processing to reduce memory usage
- Improve progress reporting with real-time metrics
- Add upload metrics tracking in new uploads table

CLI Refactoring:
- Restructure CLI to use subcommands: snapshot create/list/purge/verify
- Add store info command for S3 configuration display
- Add custom duration parser supporting days/weeks/months/years
- Remove old backup.go in favor of enhanced snapshot.go
- Add --cron flag for silent operation

Configuration Changes:
- Remove unused index_prefix configuration option
- Add support for snapshot pruning retention policies
- Improve configuration validation and error messages

Testing Improvements:
- Add comprehensive repository tests with edge cases
- Add cascade delete debugging tests
- Fix concurrent operation tests to use SQLite busy timeout
- Remove tolerance for SQLITE_BUSY errors in tests

Documentation:
- Add MIT LICENSE file
- Update README with new command structure
- Add comprehensive DATAMODEL.md explaining database schema
- Update DESIGN.md with UUID-based architecture

Other Changes:
- Add test-config.yml for testing
- Update Makefile with better test output formatting
- Fix various race conditions in concurrent operations
- Improve error handling throughout

internal/config/config.go

@@ -9,7 +9,10 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
-// Config represents the application configuration
+// Config represents the application configuration for Vaultik.
+// It defines all settings for backup operations, including source directories,
+// encryption recipients, S3 storage configuration, and performance tuning parameters.
+// Configuration is typically loaded from a YAML file.
 type Config struct {
 	AgeRecipients     []string      `yaml:"age_recipients"`
 	BackupInterval    time.Duration `yaml:"backup_interval"`
@@ -19,14 +22,15 @@ type Config struct {
 	FullScanInterval  time.Duration `yaml:"full_scan_interval"`
 	Hostname          string        `yaml:"hostname"`
 	IndexPath         string        `yaml:"index_path"`
-	IndexPrefix       string        `yaml:"index_prefix"`
 	MinTimeBetweenRun time.Duration `yaml:"min_time_between_run"`
 	S3                S3Config      `yaml:"s3"`
 	SourceDirs        []string      `yaml:"source_dirs"`
 	CompressionLevel  int           `yaml:"compression_level"`
 }
 
-// S3Config represents S3 storage configuration
+// S3Config represents S3 storage configuration for backup storage.
+// It supports both AWS S3 and S3-compatible storage services.
+// All fields except UseSSL and PartSize are required.
 type S3Config struct {
 	Endpoint        string `yaml:"endpoint"`
 	Bucket          string `yaml:"bucket"`
@@ -38,10 +42,14 @@ type S3Config struct {
 	PartSize        Size   `yaml:"part_size"`
 }
 
-// ConfigPath wraps the config file path for fx injection
+// ConfigPath wraps the config file path for fx dependency injection.
+// This type allows the config file path to be injected as a distinct type
+// rather than a plain string, avoiding conflicts with other string dependencies.
 type ConfigPath string
 
-// New creates a new Config instance
+// New creates a new Config instance by loading from the specified path.
+// This function is used by the fx dependency injection framework.
+// Returns an error if the path is empty or if loading fails.
 func New(path ConfigPath) (*Config, error) {
 	if path == "" {
 		return nil, fmt.Errorf("config path not provided")
@@ -55,7 +63,11 @@ func New(path ConfigPath) (*Config, error) {
 	return cfg, nil
 }
 
-// Load reads and parses the configuration file
+// Load reads and parses the configuration file from the specified path.
+// It applies default values for optional fields, performs environment variable
+// substitution for certain fields (like IndexPath), and validates the configuration.
+// The configuration file should be in YAML format. Returns an error if the file
+// cannot be read, parsed, or if validation fails.
 func Load(path string) (*Config, error) {
 	data, err := os.ReadFile(path)
 	if err != nil {
@@ -70,7 +82,6 @@ func Load(path string) (*Config, error) {
 		FullScanInterval:  24 * time.Hour,
 		MinTimeBetweenRun: 15 * time.Minute,
 		IndexPath:         "/var/lib/vaultik/index.sqlite",
-		IndexPrefix:       "index/",
 		CompressionLevel:  3,
 	}
 
@@ -107,7 +118,15 @@ func Load(path string) (*Config, error) {
 	return cfg, nil
 }
 
-// Validate checks if the configuration is valid
+// Validate checks if the configuration is valid and complete.
+// It ensures all required fields are present and have valid values:
+// - At least one age recipient must be specified
+// - At least one source directory must be configured
+// - S3 credentials and endpoint must be provided
+// - Chunk size must be at least 1MB
+// - Blob size limit must be at least the chunk size
+// - Compression level must be between 1 and 19
+// Returns an error describing the first validation failure encountered.
 func (c *Config) Validate() error {
 	if len(c.AgeRecipients) == 0 {
 		return fmt.Errorf("at least one age_recipient is required")
@@ -148,7 +167,8 @@ func (c *Config) Validate() error {
 	return nil
 }
 
-// Module exports the config module for fx
+// Module exports the config module for fx dependency injection.
+// It provides the Config type to other modules in the application.
 var Module = fx.Module("config",
 	fx.Provide(New),
 )