#921 Guard against divide-by-zero in visualizationUtils.calculateTren…

[Kappa16]

CLOSE #921

Title: Guard against divide-by-zero in visualizationUtils.calculateTrend FIXED

Description

Fixes a division-by-zero in calculateTrend (src/utils/visualizationUtils.ts) where change = ((last - first) / first) * 100 produced Infinity/-Infinity/NaN when the first data point is 0 (common for new metrics), and absurd percentages (e.g. ~5e14%) for near-zero baselines. Dashboards consuming useDataVisualization().calculateStats() rendered nonsensical trends as a result.

Changes (2 files, +62/-0):

• src/utils/visualizationUtils.ts — added a zero/near-zero guard (Number.EPSILON) before the division: both endpoints ≈ 0 → { neutral, 0 }; zero baseline with movement → direction of movement with a finite conventional 100% fallback. All other inputs use the unchanged original formula (no breaking changes).
• src/utils/__tests__/visualizationUtils.test.ts — 5 new regression tests (zero-baseline up/down, 0→0 NaN case, near-zero baseline, both-endpoints-near-zero).

Validation: module tests 31/31 ✓ · tsc --noEmit exit 0 ✓ · ESLint 0 errors ✓ · Prettier clean ✓ · full pnpm run build green (compile ✓, 71/71 static pages ✓) ✓ · full workspace suite run with zero regressions attributable to this change (pre-existing failures in unrelated files A/B-verified against pristine HEAD) ✓.

Related Issue

src/utils/visualizationUtils.ts calculateTrend (lines 236–238) — division by first === 0 yields Infinity/NaN and nonsensical trend in dashboards (zero/near-zero guard required before dividing).

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Checklist

• Code follows project style guidelines (ESLint 0 errors, Prettier --check clean on both touched files)
• Self-review completed (diff reviewed: minimal +18/+44, original formula untouched for non-zero baselines)
• No console errors (no console statements added; build + type-check + tests all clean)
• Uses Lucide icons consistently (N/A — no UI/icon changes)
• Responsive design implemented (N/A — no UI changes; logic-only utility fix)
• Starknet best practices followed (N/A — no Web3/Starknet code paths touched)

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