Feature Request: Select existing client to auto-populate data when creating invoices

[felipep]

Is your feature request related to a problem? Please describe.

When creating a new invoice in solidtime, users currently have to manually enter all client details (name, address, VAT number, etc.) every single time. This repetitive task is time-consuming, tedious, and increases the risk of typos.

Describe the solution you'd like

It would be a huge usability improvement to be able to select an existing client from the database when creating a new invoice.
Ideally, there should be a dropdown menu or search field like "Select Client" on the invoice creation screen. Once a client is selected, all the relevant billing information should automatically populate the corresponding fields on the invoice.

Describe alternatives you've considered

The only current alternative is manually copy-pasting the client's information from previous invoices, an external CRM, or a text document, which slows down the billing process significantly.

Additional context

A smooth and fast invoicing process is key for a time-tracking and billing tool. Being able to store client profiles and reuse them for recurring billing is a fundamental feature that users expect when switching from other tools like Harvest or Toggl. Implementing this would greatly enhance the user experience.