feat: add outlet direction (horizontal/vertical), wall light styles, floor textures, and stretch ceiling

- Add configurable outlet direction (horizontal/vertical) stored in metadata
- Add wall light style variants (classic, pendant-globe, sconce-up, sconce-down)
- Add PBR floor textures including natural oak
- Add stretch ceiling offset support with DB migration
- Add furniture surface texture selection
- Add canvas theme colors utility for dark mode support
- Update projection views with improved rendering
- Add EN and RU translations for all new properties

apps/server/prisma/schema.prisma

@@ -27,6 +27,11 @@ model Room {
   wallHeight      Float           @default(2.7)
   plinthHeight    Float           @default(0.06)
   plinthThickness Float           @default(0.01)
+  /// Distance (meters) the stretch ceiling hangs *below* the structural
+  /// ceiling. 0 = no stretch ceiling. The ceiling plane is therefore at
+  /// `wallHeight - stretchCeilingOffset`. Display-only: does not affect
+  /// wall geometry, opening positions, or electrical elevations.
+  stretchCeilingOffset Float      @default(0)
   order           Int             @default(0)
   posX            Float           @default(0)
   posY            Float           @default(0)