Move WLED config tips to footer, add Web UI link, move preview to calibration

- Move WLED Configuration tips from Add Device modal to page footer
- Add WLED Web UI link in footer (auto-populated with first device URL)
- Add WLED Web UI button (globe icon) to device card actions
- Move pixel preview button from device card to calibration modal footer
- Add en/ru i18n keys for new UI elements

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/style.css

@@ -794,6 +794,20 @@ input:-webkit-autofill:focus {
     margin: 0;
 }
 
+.footer-tip {
+    margin-bottom: 12px !important;
+    padding: 10px 16px;
+    background: rgba(33, 150, 243, 0.08);
+    border-radius: 6px;
+    font-size: 0.85rem;
+    display: inline-block;
+}
+
+.footer-tip a {
+    color: var(--info-color) !important;
+    text-decoration: underline;
+}
+
 .footer-content strong {
     color: var(--text-color);
 }