`tmpo import` Command

[DylanDevelops]

The feature request

We currently have an export command (internal/export/) that supports both CSV and JSON formats. However, there is no way to merge data or restore from a JSON/CSV backup.

Proposed solution

Create cmd/import.go. Use the internal/export package structures (like ExportEntry in json.go) to parse an input file, and batch insert them using db.CreateManualEntry.

Additional context

No response