[Chore] Speed up frontend CI dependency setup

[openroomote-bruno]

​Created by Roomote. View the task or mention @roomote for follow-up asks.

What changed

Make the shared frontend dependency cache specific to bun.lock. Frontend-capable CI jobs now skip bun install --frozen-lockfile when that exact cache is restored, while still installing after a fallback or cache miss.

Why this change was made

The reusable frontend setup is used by 42 workflow jobs across 32 CI workflows. Running a frozen install after every exact node_modules cache restore duplicates work without improving the resolved dependency tree.

Impact

Exact cache hits avoid the dependency-install step while preserving package patching. A lockfile change produces a new primary cache key and fallback caches still run the frozen install, so dependency updates remain correct. YAML parsing and whitespace checks pass; actionlint is unavailable in this environment.