fix(web): hooks-warnings batch 1 — static-components, purity, immutability to zero

[okieselbach]

Summary

First burn-down batch of the React-Compiler hooks warnings: 163 → 141, CI --max-warnings ratchet lowered to match. Targets the categories with real bug risk per finding, per the agreed prioritization.

static-components (14 → 0) — real remount bugs: SortIcon (geographic-performance), SortIndicator (VulnerabilityReportSection) and SearchIcon/ResultsDropdown (GlobalSearch) were defined inside render — a new component type on every render, so React unmounted and rebuilt their subtrees each time (GlobalSearch tore down its results dropdown on every keystroke). All hoisted to module level with explicit props.

purity (6 → 0): Date.now() during render replaced with mount-time clocks (useState lazy init) for the date-input caps (Maintenance sections) and trial-expiry checks (TenantManagement, SectionTenantConfigReport). FeedbackSection refreshes its clock per fetch so the "Xm ago" labels track the data they describe. DownloadProgress falls back to NaN instead of wall-clock for unparseable event timestamps (the rate calculation already guards via Number.isFinite).

immutability (5 → 0): fetch functions were declared below the effects that call them (diagnosis, fleet-health, DistressReports) — moved above the effects, no other changes.

Note: the immutability fixes unblocked deeper compiler analysis in those 3 files, surfacing 3 latent set-state-in-effect findings (93 → 96). They belong to the set-state category and stay for its own batch — nothing got worse, it just became visible.

Verification

• eslint: 0 errors / exactly 141 warnings — gate command exits 0
• tsc --noEmit clean, vitest 611/611, static export builds

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