Problem: UI appeared as narrow dark panel on white background with scrollbar.
Root causes:
- html/body had no reset — default browser margin/padding = white borders
- index.html referenced non-existent /style.css
- .app used height:100vh but no width:100vw or overflow:hidden
- sidebar used fixed width instead of flexbox
Fixed:
- index.html: added critical CSS reset (html/body/#app = 100%, margin:0, overflow:hidden, dark bg)
- index.html: removed /style.css ref, changed lang to ru, title to Верстак
- App.svelte: complete layout rewrite
- .app = flex, 100vw x 100vh, overflow:hidden
- sidebar = 260px width, full height, flex column
- main = flex:1, full height, flex column (header + content)
- sidebar nav with sections + nodes using <button> elements
- content area fills remaining space
- proper dark theme colors throughout
- Rebuilt frontend/dist and cmd/verstak-gui/frontend-dist