Refactor docker-compose: single deployable file + local override

- docker-compose.yml is now the single file for Portainer (staging and prod).
  Uses registry images with ${IMAGE_TAG:-staging}, ${LOGS_PATH:-/opt/myai/logs},
  and ${FILES_PATH:-/opt/myai/files} so the same file works for all environments.
- docker-compose.override.yml adds build context, ports, and env_file for local dev
  and is auto-merged by "docker compose up" (no extra flags needed).
- .env.template documents IMAGE_TAG, LOGS_PATH, FILES_PATH alongside existing vars.
- docker-compose.dcproj updated so override file nests under docker-compose.yml in
  Solution Explorer.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose/docker-compose.dcproj

@@ -20,5 +20,8 @@
       <DependentUpon>.env</DependentUpon>
     </None>
     <None Include="docker-compose.yml" />
+    <None Include="docker-compose.override.yml">
+      <DependentUpon>docker-compose.yml</DependentUpon>
+    </None>
   </ItemGroup>
 </Project>