feat: Add timezone setting in preferences + clickable logo

- Add timezone dropdown to settings modal with common timezones
- Save/load timezone preference per user
- Apply user's timezone preference after authentication
- Override system default with user preference if set
- Make dashboard logo clickable (returns to default filters)
- Show current timezone in settings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

assets/js/settings.js

@@ -45,6 +45,13 @@ function applyPreferences() {
         document.body.classList.add(`table-${density}`);
     }
 
+    // Timezone - use server default if not set
+    const timezone = userPreferences.timezone || window.APP_TIMEZONE || 'America/New_York';
+    const timezoneSelect = document.getElementById('userTimezone');
+    if (timezoneSelect) {
+        timezoneSelect.value = timezone;
+    }
+
     // Notifications
     const notificationsCheckbox = document.getElementById('notificationsEnabled');
     if (notificationsCheckbox) {
@@ -71,6 +78,7 @@ async function saveSettings() {
         default_status_filters: Array.from(document.querySelectorAll('[name="defaultFilters"]:checked'))
             .map(cb => cb.value).join(','),
         table_density: document.getElementById('tableDensity').value,
+        timezone: document.getElementById('userTimezone').value,
         notifications_enabled: document.getElementById('notificationsEnabled').checked ? '1' : '0',
         sound_effects: document.getElementById('soundEffects').checked ? '1' : '0',
         toast_duration: document.getElementById('toastDuration').value