Cover the service-resources web helpers and hooks

[selfcontained]

Summary

• Adds the first unit coverage for the Add service resources dashboard #823 service-resources web side (the server side already has service-resources.test.ts + subsystem-tracker.test.ts; the web helpers/hooks had zero tests).
• service-resources-format.test.ts (18 tests): formatBytes null/—, <1024 passthrough, KB→TB unit ladder incl. the above-TB clamp, and the >=10 → toFixed(0) vs toFixed(1) decimal threshold; formatMs null/<1 ms/rounding/seconds branches; formatUptime d+h / h+m / m-only tiers; stateLabel degraded special case; the full 7-state stateBadgeVariant mapping; metadataLabel camelCase splitting.
• use-service-resources.test.tsx (9 tests): per-window query keys and request URLs, placeholder data retained across window switches, mutation POST payload asserted from the actual request body, optimistic disable clearing series/history across every cached window, optimistic enable preserving history, empty-cache no-op, full rollback on POST failure, and post-settle invalidation.

Verification

• 13-mutant battery against both source files: 13/13 caught (unit thresholds, branch drops, hardcoded window, optimistic-update gate, rollback loop, invalidation, POST payload, placeholderData).
• One general review agent pass on the diff; its must-fix (explicit RTL cleanup() in afterEach — this repo has no vitest auto-cleanup, and a mounted observer's 15s refetchInterval could consume a later test's mock queue) and nits (mutations wrapped in act(), dropped an impossible-cast assertion, fixed a mischaracterized test name) are applied.
• pnpm run check, full unit suite (web 416 pass), pnpm run finalize:web, pnpm run lint:web (0 errors), E2E 170 pass / 12 skip — all green locally.

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