feat(usage): add All Time period option and refine overview cards

- Add "all" period option to usage dashboard and chart API
- Aggregate all days in getChartData when period is "all"
- Center overview card metrics and adjust font size to prevent truncation

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

src/shared/components/UsageStats.js

@@ -200,6 +200,7 @@ const PERIODS = [
   { value: "7d", label: "7D" },
   { value: "30d", label: "30D" },
   { value: "60d", label: "60D" },
+  { value: "all", label: "All" },
 ];
 
 export default function UsageStats({ period: periodProp, setPeriod: setPeriodProp, hidePeriodSelector = false } = {}) {
@@ -448,7 +449,7 @@ export default function UsageStats({ period: periodProp, setPeriod: setPeriodPro
       {/* Period selector (hidden when controlled by parent) */}
       {!hidePeriodSelector && (
         <div className="flex w-full items-center gap-2 sm:w-auto sm:self-end">
-          <div className="grid flex-1 grid-cols-5 items-center gap-1 rounded-lg border border-border bg-bg-subtle p-1 sm:flex sm:flex-none">
+          <div className="grid flex-1 grid-cols-6 items-center gap-1 rounded-lg border border-border bg-bg-subtle p-1 sm:flex sm:flex-none">
             {PERIODS.map((p) => (
               <button
                 key={p.value}