feat(fence): add height selection for fence panels and update related logic

- Introduced a new section in the UI for selecting fence heights, visible only when the fence option is enabled.
- Updated the fence label to clarify the presence of gates.
- Enhanced the JavaScript logic to manage the visibility of fence heights based on user selection.
- Modified the fence rendering logic to accommodate different heights and ensure proper visibility based on the selected height.
- Updated CSS to style the new fence height controls appropriately.
- Adjusted the model configuration to reflect changes in the fence height options.

locenice/css/web.css

@@ -18,3 +18,7 @@ body.interior-active #projectToggle{top:76px;left:25px}
 @media(max-height:550px){#projectToggle{top:auto;bottom:120px}}
 
 @media(max-width:850px){body.std-open #webStatus{display:none}}
+
+/* Výška plotu: druhá řada pod přepínači okolí, jen při zapnutém plotu. */
+.fence-heights[hidden]{display:none}.fence-heights{gap:3px}.fence-heights-label{font-size:10px;color:#6e8066;padding:0 6px 0 5px;white-space:nowrap}.fence-heights button.site-switch{background:transparent;font-family:inherit;line-height:1.1}.fence-heights button.site-switch.selected{background:#e1ecdc}
+@media(max-width:520px){.fence-heights-label{font-size:9px;padding:0 3px}.fence-heights button.site-switch{padding:8px 5px}}