Align detail panel top edge with the header's actual bottom edge

DetailPanelOverlay.vue (shared by the shot/asset/task detail panels and
the My Tasks page) used a hardcoded top-[113px] that left a 49px gap
above the panel. The header is h-16 (64px), confirmed via its live
getBoundingClientRect() - switched to top-16 so the panel's top edge
sits flush against it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/shared/DetailPanelOverlay.vue

@@ -21,7 +21,7 @@ const emit = defineEmits<{ 'update:mobileOpen': [value: boolean] }>()
   >
     <div
       v-if="visible"
-      class="fixed right-0 top-[113px] bottom-0 w-96 bg-background border-l shadow-lg z-50 hidden lg:block overflow-y-auto"
+      class="fixed right-0 top-16 bottom-0 w-96 bg-background border-l shadow-lg z-50 hidden lg:block overflow-y-auto"
     >
       <slot />
     </div>