Improve Web UI with footer, icon buttons, and better modals

- Add footer with author info (name, email, git repository link)
- Replace device action buttons with icons to save space:
  - Start/Stop: ▶️/⏹️, Settings: ⚙️, Calibrate: 📐, Remove: 🗑️
  - Added hover tooltips with translated text
  - Added btn-icon CSS class for compact styling
- Replace native browser confirm() with custom modal dialog:
  - Matches app theme and supports translations
  - Used for logout and device removal confirmations
  - Added confirm.title, confirm.yes, confirm.no translations
- Disable background scrolling when modals are open:
  - Added modal-open class to body when any modal opens
  - Prevents page scroll behind modals for better UX
  - Applied to all modals: login, settings, calibration, confirmation

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

server/src/wled_controller/static/style.css

@@ -44,6 +44,10 @@ body {
     line-height: 1.6;
 }
 
+body.modal-open {
+    overflow: hidden;
+}
+
 .container {
     max-width: 1200px;
     margin: 0 auto;
@@ -218,6 +222,18 @@ section {
     color: var(--text-color);
 }
 
+.btn-icon {
+    min-width: auto;
+    padding: 8px 12px;
+    font-size: 1.2rem;
+    flex: 0 0 auto;
+}
+
+.btn-icon:hover {
+    transform: scale(1.1);
+    opacity: 1;
+}
+
 .display-card {
     background: var(--card-bg);
     border: 1px solid var(--border-color);
@@ -620,6 +636,38 @@ input:-webkit-autofill:focus {
     transform: scale(1.1);
 }
 
+/* Footer */
+.app-footer {
+    margin-top: 60px;
+    padding: 30px 0;
+    border-top: 1px solid var(--border-color);
+    text-align: center;
+}
+
+.footer-content {
+    color: var(--text-secondary);
+    font-size: 0.9rem;
+}
+
+.footer-content p {
+    margin: 0;
+}
+
+.footer-content strong {
+    color: var(--text-color);
+}
+
+.footer-content a {
+    color: var(--primary-color);
+    text-decoration: none;
+    transition: opacity 0.2s;
+}
+
+.footer-content a:hover {
+    opacity: 0.8;
+    text-decoration: underline;
+}
+
 @media (max-width: 768px) {
     .displays-grid,
     .devices-grid {