test: Add floating navigation buttons to diagnose offcanvas issue

Added semi-transparent floating buttons under navbar to test
if viewport corruption is caused by offcanvas menu or navigation itself.

Changes:
- Add floating-test-buttons div in index.html
- Two buttons: DM and Contacts (using navigateTo())
- Sticky position under navbar
- Semi-transparent background with backdrop blur
- Centered layout with gap between buttons

Test scenario:
1. Click floating buttons (bypass offcanvas menu)
2. Navigate to DM / Contact Management
3. Return to main page via Home button
4. Check if status bar is still visible

If floating buttons work correctly:
- Problem is in offcanvas menu cleanup
- Can keep these buttons as permanent quick navigation

If floating buttons also cause corruption:
- Problem is deeper (viewport/layout issue)
- Need different approach

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/static/css/style.css

@@ -580,6 +580,29 @@ main {
     box-shadow: 0 8px 16px rgba(0, 0, 0, 0.3);
 }
 
+/* =============================================================================
+   TEST: Floating Navigation Buttons
+   ============================================================================= */
+
+.floating-test-buttons {
+    position: sticky;
+    top: 0;
+    z-index: 999;
+    background: rgba(255, 255, 255, 0.85);
+    backdrop-filter: blur(10px);
+    padding: 0.5rem;
+    display: flex;
+    gap: 0.5rem;
+    justify-content: center;
+    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
+    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+}
+
+.floating-test-buttons .btn {
+    min-width: 100px;
+    font-weight: 500;
+}
+
 /* =============================================================================
    PWA Safe Area Handling
    ============================================================================= */