feat: Complete tablet UI overhaul with popup menu system and help bubble

Major Changes:
- 🪟 Popup Menu System: Converted slide-down navigation to draggable, minimizable popup window
- ❓ Help Bubble: Added contextual help system for admin dashboard (accessible via ? bubble)
- 🎨 Universal Theme Engine: All elements now properly match selected theme across all panels
- 📱 Enhanced Tablet Support: Comprehensive touch gestures, handwriting recognition, and Apple Pencil optimization
- 🖊️ Unified Write Mode: Combined handwriting and keyboard input with large canvas interface

Technical Implementation:
- Draggable popup with minimize/restore functionality and boundary constraints
- Dynamic theme switching using CSS variables throughout all components
- Help system with modal overlay and keyboard shortcuts (ESC to close)
- Responsive design optimizations for mobile, tablet, and desktop
- Comprehensive CSS overrides to eliminate hardcoded colors
- JavaScript fixes for canvas stroke colors and input styling

UI/UX Improvements:
- Clean admin dashboard without instruction clutter
- Professional popup interface with smooth animations
- Better contrast and readability across all themes (default, playground, chalkboard, galaxy, nature)
- Improved accessibility with proper focus management
- Enhanced mobile responsiveness with touch-optimized controls

Files Modified:
- Menu system: tablet-menu.js, tablet-menu.css
- Theme engine: styles.css, themes integration
- Admin interface: index.html, ui.js
- Input systems: game.js, unified-write.js, handwriting.js
- Authentication: auth.js with tablet menu cleanup

public/js/gamification.js

@@ -167,12 +167,12 @@ async function completeChallenge(challengeId, challengeType) {
 // Render streak indicator in student panel
 function renderStreakIndicator() {
   const streakContainer = document.getElementById('streakContainer');
-  if (!streakContainer || !userProgress) return;
+  if (!streakContainer) return;
   
   // Clear previous content
   streakContainer.innerHTML = '';
   
-  const currentStreak = userProgress.streaks.current || 0;
+  const currentStreak = userProgress?.streaks?.current || 0;
   
   // Create streak element
   const streakEl = document.createElement('div');
@@ -191,7 +191,7 @@ function renderStreakIndicator() {
     </div>
     <div class="streak-record">
       <div class="streak-subtitle">Best</div>
-      <div class="streak-best">${userProgress.streaks.longest || 0}</div>
+      <div class="streak-best">${userProgress?.streaks?.longest || 0}</div>
     </div>
   `;
   
@@ -201,7 +201,7 @@ function renderStreakIndicator() {
 // Render user stats in student panel
 function renderUserStats() {
   const statsContainer = document.getElementById('userStatsContainer');
-  if (!statsContainer || !userProgress) return;
+  if (!statsContainer) return;
   
   // Clear previous content
   statsContainer.innerHTML = '';
@@ -213,19 +213,19 @@ function renderUserStats() {
   // Add stat cards
   statsEl.innerHTML = `
     <div class="stat-card">
-      <div class="stat-value">${userProgress.stats.points || 0}</div>
+      <div class="stat-value">${userProgress?.stats?.points || 0}</div>
       <div class="stat-label">Points</div>
     </div>
     <div class="stat-card">
-      <div class="stat-value">${userProgress.stats.accuracy ? userProgress.stats.accuracy.toFixed(1) + '%' : '0%'}</div>
+      <div class="stat-value">${userProgress?.stats?.accuracy ? userProgress.stats.accuracy.toFixed(1) + '%' : '0%'}</div>
       <div class="stat-label">Accuracy</div>
     </div>
     <div class="stat-card">
-      <div class="stat-value">${userProgress.stats.totalSessions || 0}</div>
+      <div class="stat-value">${userProgress?.stats?.totalSessions || 0}</div>
       <div class="stat-label">Sessions</div>
     </div>
     <div class="stat-card">
-      <div class="stat-value">${userProgress.stats.totalWords || 0}</div>
+      <div class="stat-value">${userProgress?.stats?.totalWords || 0}</div>
       <div class="stat-label">Words</div>
     </div>
   `;
@@ -233,6 +233,21 @@ function renderUserStats() {
   statsContainer.appendChild(statsEl);
 }
 
+// Initialize containers with default content
+function initializeStudentContainers() {
+  // Initialize streak container immediately
+  const streakContainer = document.getElementById('streakContainer');
+  if (streakContainer && !streakContainer.innerHTML.trim()) {
+    renderStreakIndicator();
+  }
+  
+  // Initialize stats container immediately
+  const statsContainer = document.getElementById('userStatsContainer');
+  if (statsContainer && !statsContainer.innerHTML.trim()) {
+    renderUserStats();
+  }
+}
+
 // Render challenges in student panel
 function renderChallenges() {
   const challengesContainer = document.getElementById('challengesContainer');