feat(api): redirect / to /docs so the HF Space App tab shows Swagger

feat(deploy): HuggingFace Spaces deploy — free 16 GB RAM alternative

fix(ci): make ruff + mypy green on the new src/ layout

refactor: replace importlib hacks with normal package imports

chore: git mv production code into src/guichetoi/

chore: scaffold src/guichetoi package, pyproject.toml, CI, PR/issue templates