feat(ui): unify header and implement navigation drawer (Task 17)

- Redesign top header into clean, uncluttered layout with hamburger drawer trigger, clickable logo, central SRS focus badge, theme toggle and profile avatar
- Implement unified responsive Navigation Drawer for both desktop and mobile with touch swipe-to-dismiss, backdrop blur, keyboard Esc support and background scroll lock
- Streamline mobile bottom tab bar to 4 core actions (Dictionary, SRS, Reader, Menu) with Menu opening the unified drawer
- Synchronize real-time SRS due badges and dictionary word statistics between header, bottom tabs, and drawer
- Eliminate obsolete separate mobile-menu-modal in favor of unified drawer
- Bump Service Worker cache version to notes-v5.7

app/static/js/modules/ui.js

@@ -139,13 +139,32 @@ export function updateHeaderStats(total = 0, today = 0, srsCount = 0) {
     const statTotal = document.getElementById('stat-total');
     const statToday = document.getElementById('stat-today');
     const srsBadge = document.getElementById('srs-badge');
+    const tabSrsBadge = document.getElementById('tab-srs-badge');
+    const drawerSrsBadge = document.getElementById('drawer-srs-badge');
+    const drawerStatTotal = document.getElementById('drawer-stat-total');
+    const drawerStatToday = document.getElementById('drawer-stat-today');
+    const drawerStatDue = document.getElementById('drawer-stat-due');
+
+    const formattedToday = today > 0 ? `+${today}` : today;
 
     if (statTotal) statTotal.textContent = total;
-    if (statToday) statToday.textContent = today;
+    if (statToday) statToday.textContent = formattedToday;
+    if (drawerStatTotal) drawerStatTotal.textContent = total;
+    if (drawerStatToday) drawerStatToday.textContent = formattedToday;
+    if (drawerStatDue) drawerStatDue.textContent = srsCount;
+
     if (srsBadge) {
         srsBadge.textContent = srsCount;
         srsBadge.style.display = srsCount > 0 ? 'inline-block' : 'none';
     }
+    if (tabSrsBadge) {
+        tabSrsBadge.textContent = srsCount;
+        tabSrsBadge.classList.toggle('hidden', srsCount === 0);
+    }
+    if (drawerSrsBadge) {
+        drawerSrsBadge.textContent = srsCount;
+        drawerSrsBadge.classList.toggle('hidden', srsCount === 0);
+    }
 }
 
 // -----------------------------------------------------------------------