feat: extract into remaining packages

There has been a cyclic dependency.
transaction
	-> treasure_chest
	-> transaction_recurring
	-> transaction

This has been temporarily solved by moving the GenerateTransactions
function into the transaction package. In the future, this function has
to be rewritten to use a proper Service insteas of direct DB access or
replaced with a different system entirely.

internal/core/log.go

@@ -0,0 +1,50 @@
+package core
+
+import (
+	"context"
+	"log/slog"
+	"os"
+
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+)
+
+func NewLogPropagator() *slog.Logger {
+	return slog.New(&logHandler{
+		console: slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{}),
+		otel:    otelslog.NewHandler("spend-sparrow"),
+	})
+}
+
+type logHandler struct {
+	console slog.Handler
+	otel    slog.Handler
+}
+
+// Enabled implements slog.Handler.
+func (l *logHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	return l.console.Enabled(ctx, level)
+}
+
+// Handle implements slog.Handler.
+func (l *logHandler) Handle(ctx context.Context, rec slog.Record) error {
+	if err := l.console.Handle(ctx, rec); err != nil {
+		return err
+	}
+	return l.otel.Handle(ctx, rec)
+}
+
+// WithAttrs implements slog.Handler.
+func (l *logHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return &logHandler{
+		console: l.console.WithAttrs(attrs),
+		otel:    l.otel.WithAttrs(attrs),
+	}
+}
+
+// WithGroup implements slog.Handler.
+func (l *logHandler) WithGroup(name string) slog.Handler {
+	return &logHandler{
+		console: l.console.WithGroup(name),
+		otel:    l.otel.WithGroup(name),
+	}
+}