feat: initialise a new totals tab with basic UI (#94)

* feat: initialise a new totals tab with basic UI

* fix: update group tabs and add stats page

* fix: styling within the new elements

* Prettier

* Display active user expenses only if active user is set

---------

Co-authored-by: Sebastien Castiel <sebastien@castiel.me>

src/app/groups/[groupId]/stats/totals-your-share.tsx

@@ -0,0 +1,34 @@
+'use client'
+import { getGroup, getGroupExpenses } from '@/lib/api'
+import { getTotalActiveUserShare } from '@/lib/totals'
+import { formatCurrency } from '@/lib/utils'
+import { useEffect, useState } from 'react'
+
+type Props = {
+  group: NonNullable<Awaited<ReturnType<typeof getGroup>>>
+  expenses: NonNullable<Awaited<ReturnType<typeof getGroupExpenses>>>
+}
+
+export function TotalsYourShare({ group, expenses }: Props) {
+  const [activeUser, setActiveUser] = useState('')
+
+  useEffect(() => {
+    const activeUser = localStorage.getItem(`${group.id}-activeUser`)
+    if (activeUser) setActiveUser(activeUser)
+  }, [group, expenses])
+
+  const totalActiveUserShare =
+    activeUser === '' || activeUser === 'None'
+      ? 0
+      : getTotalActiveUserShare(activeUser, expenses)
+  const currency = group.currency
+
+  return (
+    <div>
+      <div className="text-muted-foreground">Your total share</div>
+      <div className="text-lg">
+        {formatCurrency(currency, totalActiveUserShare)}
+      </div>
+    </div>
+  )
+}