fix: eslint findings

Remove dead code and unused imports, drop useless assignments, and tune
rules in eslint.config.js (underscore-prefixed unused names, intentional BOM/NBSP,
React Compiler rules from eslint-plugin-react-hooks 7 as warnings).

src/views/NewInvoice.tsx

@@ -48,8 +48,7 @@ import type {
   Settings,
   TaxType,
 } from "../lib/types";
-import { computeLineAmount, computeTotals } from "../lib/invoice";
-import { amountInWords } from "../lib/numberToWords";
+import { computeLineAmount } from "../lib/invoice";
 import { gstinFullError } from "../lib/validators";
 import { addDays, formatAmount, todayIso } from "../lib/format";
 import { modelFromAssets, prefsForInvoice } from "../lib/pdf";
@@ -256,11 +255,6 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
       ? "cgst_sgst"
       : "igst";
   const clientGstinError = gstinFullError(clientGstin);
-  const totals = useMemo(
-    () => computeTotals(items, discount, effectiveTaxType, taxRate),
-    [items, discount, effectiveTaxType, taxRate],
-  );
-  const words = useMemo(() => amountInWords(totals.total), [totals.total]);
   const bank = useMemo(() => banks.find((b) => b.id === bankId) ?? null, [banks, bankId]);
 
   const payload = useMemo(