Migrate dotfiles repo path from ~/dev/dotfiles to ~/.dotfiles

[lemtoc]

Context

Planning to reorganize ~/dev/ into work/private/oss categories. Since dotfiles doesn't belong to any category, move it to ~/.dotfiles.

Changes

flake.nix

• L50, L64, L76: $HOME/dev/dotfiles → $HOME/.dotfiles

README.md

• L23, L30, L47, L61: ~/dev/dotfiles → ~/.dotfiles

Files confirmed unchanged

• hosts/common/default.nix — home directory reference, not repo path
• hosts/M4Pro/default.nix — certificate path reference
• .github/actions/setup-bench-env/action.yml — CI home directory setup