fix: use section ID for reliable beacon positioning

- Add sectionId to SearchResult interface
- Search handler now looks up section by ID first
- Falls back to code/name lookup for backwards compatibility
- Fixes beacon offset in Room B (duplicate section codes)

frontend/src/components/facility3d/PlantSearch.tsx

@@ -9,6 +9,7 @@ interface SearchResult {
     sublabel: string;
     roomName: string;
     sectionCode: string;
+    sectionId: string; // For reliable section lookup
     position: {
         roomX: number;
         roomY: number;
@@ -53,6 +54,7 @@ export function PlantSearch({ floorData, onSelectResult, onHighlightResults }: P
                             sublabel: `${pos.plant.strain || 'Unknown'} • ${pos.plant.stage || 'N/A'}`,
                             roomName: room.name,
                             sectionCode: section.code || section.name,
+                            sectionId: section.id, // Added for reliable lookup
                             position: {
                                 roomX: room.posX,
                                 roomY: room.posY,

frontend/src/pages/Facility3DViewerPage.tsx

@@ -233,10 +233,24 @@ export default function Facility3DViewerPage() {
     const handleSearchSelect = useCallback((result: any) => {
         if (!floorData) return;
 
-        // Find the actual section to use grid-based position calculation
-        const room = floorData.rooms.find(r => r.name === result.roomName);
-        const section = room?.sections.find(s => (s.code || s.name) === result.sectionCode);
-        if (!section) return;
+        // Find the section - prefer ID lookup for reliability, fall back to code/name
+        let section: Section3D | undefined;
+        for (const room of floorData.rooms) {
+            if (result.sectionId) {
+                section = room.sections.find(s => s.id === result.sectionId);
+            } else {
+                // Fallback: must match both room and section code
+                if (room.name === result.roomName) {
+                    section = room.sections.find(s => (s.code || s.name) === result.sectionCode);
+                }
+            }
+            if (section) break;
+        }
+
+        if (!section) {
+            console.warn('[handleSearchSelect] Could not find section for result:', result);
+            return;
+        }
 
         const { x, y, z } = calculatePlantCoords(
             section,