fix: bypass broken Nexus, use nuget.org + local proto build

- NuGet.config: nuget.org for standard packages, local nupkg for proto
- Dockerfile: COPY nupkg/ before restore
- CI: build proto from CMS source before Docker build

src/FrontOffice.Main/NuGet.config

@@ -2,15 +2,10 @@
 <configuration>
   <packageSources>
     <clear />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
     <!-- Local packages (dev builds) -->
     <add key="Local" value="/home/masoud/Apps/project/FourSat/nupkg" />
-    <!-- Nexus (hosts FourSat packages + proxies nuget.org) -->
-    <add key="Nexus" value="http://194.5.195.53:32081/repository/nuget-all/index.json" allowInsecureConnections="true" />
+    <!-- Local packages (CI Docker builds) -->
+    <add key="LocalCI" value="nupkg" />
   </packageSources>
-  <packageSourceCredentials>
-    <Nexus>
-      <add key="Username" value="admin" />
-      <add key="ClearTextPassword" value="87zH26nbqT" />
-    </Nexus>
-  </packageSourceCredentials>
 </configuration>