Add BetterCam engine, UI polish, and bug fixes

- Add BetterCam capture engine (DXGI Desktop Duplication, priority 4)
- Fix missing picture_stream_id in get_device endpoint
- Fix template delete validation to check streams instead of devices
- Add description field to capture engine template UI
- Default template name changed to "Default" with descriptive text
- Display picker highlights selected display instead of primary
- Fix modals closing when dragging text selection outside dialog
- Rename "Engine Configuration" to "Configuration", hide when empty
- Rename "Run Test" to "Run" across all test buttons
- Always reserve space for vertical scrollbar
- Redesign Stream Settings info panel with pill-style props
- Fix processed stream showing internal ID instead of stream name
- Update en/ru locale files

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

server/src/wled_controller/static/style.css

@@ -37,6 +37,7 @@ body {
 
 html {
     background: var(--bg-color);
+    overflow-y: scroll;
 }
 
 body {
@@ -2159,23 +2160,11 @@ input:-webkit-autofill:focus {
 
 /* Stream info panel in stream selector modal */
 .stream-info-panel {
-    background: var(--bg-secondary, #2a2a2a);
-    border: 1px solid var(--border-color);
-    border-radius: 8px;
-    padding: 12px 16px;
-    margin-top: 12px;
+    padding: 4px 0 0 0;
     font-size: 14px;
     line-height: 1.6;
 }
 
-.stream-info-panel div {
-    margin-bottom: 4px;
-}
-
-.stream-info-panel strong {
-    margin-right: 6px;
-}
-
 /* Stream sub-tabs */
 .stream-tab-bar {
     display: flex;
@@ -2359,6 +2348,8 @@ input:-webkit-autofill:focus {
 
 .layout-display-pickable {
     cursor: pointer !important;
+    border: 2px solid var(--border-color) !important;
+    background: linear-gradient(135deg, rgba(128, 128, 128, 0.08), rgba(128, 128, 128, 0.03)) !important;
 }
 
 .layout-display-pickable:hover {
@@ -2366,6 +2357,12 @@ input:-webkit-autofill:focus {
     border-color: var(--primary-color) !important;
 }
 
+.layout-display-pickable.selected {
+    border-color: var(--primary-color) !important;
+    box-shadow: 0 0 16px rgba(76, 175, 80, 0.5);
+    background: rgba(76, 175, 80, 0.12) !important;
+}
+
 /* Display picker button in forms */
 .btn-display-picker {
     width: 100%;