reset mobile context caches on user identity changes

apps/mobile/src/contexts/StatisticsContext.tsx

@@ -1,4 +1,10 @@
-import React, { createContext, useContext, useState, useCallback } from "react";
+import React, {
+  createContext,
+  useContext,
+  useState,
+  useCallback,
+  useEffect,
+} from "react";
 import { useUser, useAuth } from "@clerk/clerk-expo";
 import { getUserStatistics } from "../api/statistics";
 import type { UserStatisticsResponse } from "../api/types";
@@ -75,11 +81,21 @@ export function StatisticsProvider({
 
   const clearCache = useCallback(() => {
     setStatistics(null);
+    setLoading(false);
     setLastFetchTime(0);
     setError(null);
     log.debug("Statistics cache cleared");
   }, []);
 
+  useEffect(() => {
+    clearCache();
+    if (user?.id) {
+      log.debug("Statistics cache reset for user", { userId: user.id });
+    } else {
+      log.debug("Statistics cache reset on sign-out");
+    }
+  }, [user?.id, clearCache]);
+
   const forceRefresh = useCallback(async () => {
     if (!user?.id) return;