uvr import should allow specifying the project name

[B-Nilson]

When importing an renv.lock using uvr import, the project name is always the default (the project directory name). We should add an arg --name like uvr init that allows specifying that.

We can then add and argument name = NULL to uvr::import()

[nbafrank]

@B-Nilson — shipped on main (commit 102044a, will ship in v0.3.5). uvr import --name <NAME> overrides the project name in uvr.toml. Defaults to the cwd basename when omitted, or preserves the existing manifest's name in merge mode. Validation rejects empty/short/illegal-char names up front so they can't slip through into TOML.