Internal state persistence (#27)

Allow us to generate year over year reports without having to rerun everything from the beginning.

Co-authored-by: Natercio Moniz <[email protected]>

cmd/any2anexoj-cli/pretty_printer_test.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"context"
 	"testing"
 	"time"
 
@@ -13,7 +12,7 @@ import (
 func TestPrettyPrinter_Render(t *testing.T) {
 	// Create test data
 	aw := internal.NewAggregatorWriter()
-	ctx := context.Background()
+	ctx := t.Context()
 
 	// Add some sample report items
 	err := aw.Write(ctx, internal.ReportItem{