Bump @mui/material and @mui/icons-material 7.3.1 -> ^9.1.1 together in
/web. They must move in lockstep (icons peer-depends on material), so
Dependabot's separate per-package PRs (#145/#146) could never go green
individually (ERESOLVE). Adds a 'mui' Dependabot group so future @mui/*
updates — including majors — are raised as one PR.
MUI v9 migration fixes (v7->v9 spans two majors):
- ListItemText: primaryTypographyProps -> slotProps.primary; fontSize
moved into sx (Typography system props removed in v9).
- Autocomplete renderInput: params.InputProps -> params.slotProps.input;
spread ...params.slotProps to retain inputLabel/htmlInput slots.
- Icons: @mui/icons-material/ErrorOutline -> ErrorOutlined (the plain
ErrorOutline export was removed in v9).
- vitest: inline @mui/material + react-transition-group so Vite resolves
v9's Transition.mjs directory import (native ESM loader can't).
Verified locally on Node 24: npm ci, npm run build, and npm test
(26 tests, 3 suites) all pass.