deploy: Traefik hosts + registry images for shop/admin/api

Publish nginx/API images from CI and deploy on the Pi with
shop.zea.lt, admin.zea.lt, and api.iled.zea.lt.

Co-authored-by: Cursor <cursoragent@cursor.com>

docker/Dockerfile.api

@@ -1,7 +1,7 @@
 FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
 WORKDIR /src
-COPY . .
-RUN dotnet restore iLED.sln
+COPY src/backend/ .
+RUN dotnet restore iLED.slnx
 RUN dotnet publish src/iLED.Api/iLED.Api.csproj -c Release -o /app/publish
 
 FROM mcr.microsoft.com/dotnet/aspnet:10.0