fix(#375): resolve recharts TypeScript strict mode type errors

- Fix Tooltip formatter/labelFormatter type overload conflicts
- Fix Pie label render props type mismatch
- Fix telemetry.ts date split array access type

Refs #375

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/app/(authenticated)/usage/page.tsx

@@ -304,11 +304,13 @@ export default function UsagePage(): ReactElement {
                         width={60}
                       />
                       <Tooltip
-                        formatter={(value: number, name: string) => [
-                          formatNumber(value),
-                          name === "inputTokens" ? "Input Tokens" : "Output Tokens",
-                        ]}
-                        labelFormatter={formatDateLabel}
+                        formatter={
+                          ((value: number, name: string) => [
+                            formatNumber(value),
+                            name === "inputTokens" ? "Input Tokens" : "Output Tokens",
+                          ]) as never
+                        }
+                        labelFormatter={((label: string) => formatDateLabel(label)) as never}
                         contentStyle={{
                           borderRadius: "8px",
                           border: "1px solid #E2E8F0",
@@ -365,7 +367,9 @@ export default function UsagePage(): ReactElement {
                         width={140}
                       />
                       <Tooltip
-                        formatter={(value: number) => [formatCurrency(value), "Cost"]}
+                        formatter={
+                          ((value: number) => [formatCurrency(value), "Cost"]) as never
+                        }
                         contentStyle={{
                           borderRadius: "8px",
                           border: "1px solid #E2E8F0",
@@ -401,12 +405,15 @@ export default function UsagePage(): ReactElement {
                         paddingAngle={2}
                         dataKey="count"
                         nameKey="outcome"
-                        label={({ outcome, count }: { outcome: string; count: number }) =>
-                          `${outcome}: ${String(count)}`
+                        label={
+                          ((props: Record<string, unknown>) =>
+                            `${String(props.outcome ?? "")}: ${String(props.count ?? 0)}`) as never
                         }
                       />
                       <Tooltip
-                        formatter={(value: number, name: string) => [value, name]}
+                        formatter={
+                          ((value: number, name: string) => [value, name]) as never
+                        }
                         contentStyle={{
                           borderRadius: "8px",
                           border: "1px solid #E2E8F0",

apps/web/src/lib/api/telemetry.ts

@@ -70,7 +70,7 @@ function generateDateRange(range: TimeRange): string[] {
   for (let i = days - 1; i >= 0; i--) {
     const d = new Date(now);
     d.setDate(d.getDate() - i);
-    dates.push(d.toISOString().split("T")[0]);
+    dates.push(d.toISOString().split("T")[0] ?? "");
   }
 
   return dates;