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/cli/root.go

@@ -1,18 +1,25 @@
 package cli
 
 import (
+	"fmt"
+	"os"
+
 	"github.com/spf13/cobra"
 )
 
-// RootFlags holds global flags
+// RootFlags holds global flags that apply to all commands.
+// These flags are defined on the root command and inherited by all subcommands.
 type RootFlags struct {
-	Verbose bool
-	Debug   bool
+	ConfigPath string
+	Verbose    bool
+	Debug      bool
 }
 
 var rootFlags RootFlags
 
-// NewRootCommand creates the root cobra command
+// NewRootCommand creates the root cobra command for the vaultik CLI.
+// It sets up the command structure, global flags, and adds all subcommands.
+// This is the main entry point for the CLI command hierarchy.
 func NewRootCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "vaultik",
@@ -24,23 +31,49 @@ on the source system.`,
 	}
 
 	// Add global flags
+	cmd.PersistentFlags().StringVar(&rootFlags.ConfigPath, "config", "", "Path to config file (default: $VAULTIK_CONFIG or /etc/vaultik/config.yml)")
 	cmd.PersistentFlags().BoolVarP(&rootFlags.Verbose, "verbose", "v", false, "Enable verbose output")
 	cmd.PersistentFlags().BoolVar(&rootFlags.Debug, "debug", false, "Enable debug output")
 
 	// Add subcommands
 	cmd.AddCommand(
-		NewBackupCommand(),
 		NewRestoreCommand(),
 		NewPruneCommand(),
 		NewVerifyCommand(),
 		NewFetchCommand(),
-		SnapshotCmd(),
+		NewStoreCommand(),
+		NewSnapshotCommand(),
 	)
 
 	return cmd
 }
 
-// GetRootFlags returns the global flags
+// GetRootFlags returns the global flags that were parsed from the command line.
+// This allows subcommands to access global flag values like verbosity and config path.
 func GetRootFlags() RootFlags {
 	return rootFlags
 }
+
+// ResolveConfigPath resolves the config file path from flags, environment, or default.
+// It checks in order: 1) --config flag, 2) VAULTIK_CONFIG environment variable,
+// 3) default location /etc/vaultik/config.yml. Returns an error if no valid
+// config file can be found through any of these methods.
+func ResolveConfigPath() (string, error) {
+	// First check global flag
+	if rootFlags.ConfigPath != "" {
+		return rootFlags.ConfigPath, nil
+	}
+
+	// Then check environment variable
+	if envPath := os.Getenv("VAULTIK_CONFIG"); envPath != "" {
+		return envPath, nil
+	}
+
+	// Finally check default location
+	defaultPath := "/etc/vaultik/config.yml"
+	if _, err := os.Stat(defaultPath); err == nil {
+		return defaultPath, nil
+	}
+
+	return "", fmt.Errorf("no config file specified, VAULTIK_CONFIG not set, and %s not found", defaultPath)
+}