Rename a concept across the code

After the team agrees on a better name, Devboxes renames the concept everywhere in the code.

  • Engineering
✳ Claude Code

hand this to devboxes: rename client to customer in src/invoices, we say customer everywhere else

Devboxes opened #64, which renames client to customer in 23 files under src/invoices and their tests. The client_id database column and the /clients API path stay, since renaming them would break stored data and integrations. Checks pass.