Improve email loading performance and fix UI issues

- Fixed refresh button icon not displaying (changed from icon prop to v-icon element)
- Reduced default email limit from 50 to 20 to improve loading speed
- Optimized cached email loading to only load most recent emails (up to limit)
- Fixed CommonJS require error in email-utils.ts (changed to ES module import)
- Added sorting to cached files to ensure newest emails are loaded first

This should significantly improve email loading performance from 578 cached files down to max 20

components/ClientEmailSection.vue

@@ -29,12 +29,12 @@
           <v-btn
             @click="loadEmailThread"
             variant="tonal"
-            icon="mdi-refresh"
             :loading="isRefreshing"
             size="small"
             color="grey-darken-4"
           >
-            <v-tooltip activator="parent">Refresh Emails</v-tooltip>
+            <v-icon>mdi-refresh</v-icon>
+            <v-tooltip activator="parent" location="bottom">Refresh Emails</v-tooltip>
           </v-btn>
           <v-spacer />
           <v-btn-group v-if="!mobile" variant="text" density="compact">