chore(frontend): restore Stryker mutation testing + ignoreStatic

Re-adds the @stryker-mutator devDeps and `test:mutation` scripts that
were dropped by the lucide-react bump commit, since the committed
`frontend-mutation.yml` nightly workflow depends on them. Also flips
`coverageAnalysis` from "all" to "perTest" and enables `ignoreStatic`
so the full run finishes in ~2 min instead of multiple hours (406 of
6077 mutants were top-level/static and would otherwise rerun the whole
test suite each).

Local wall time: 1 min 50 seconds.
Mutation score: 6.88% total, 60.53% of covered mutants killed
(391 killed, 255 survived, 5036 no-coverage, 0 timeout, 0 errors).
High-scoring files: secret.utils.ts (100%), pipeline-throughput.utils.ts
(96.88%), message-table-helpers.ts (92%), unit.ts (86.17%), string.ts
(84.91%), name.utils.ts (72.73%).

Author: malinskibeniamin