feat: add Docker infrastructure for 8-node cluster topology (2 central + 3 sites)

Multi-stage Dockerfile with NuGet restore layer caching, per-node appsettings
with Docker hostnames, shared bridge network with infra services, and
build/deploy/teardown scripts. Ports use 90xx block to avoid conflicts.

infra/docker-compose.yml

@@ -16,6 +16,8 @@ services:
       --gn=5
       --nf=/app/config/nodes.json
       --pn=50000
+    networks:
+      - scadalink-net
     restart: unless-stopped
 
   ldap:
@@ -25,6 +27,8 @@ services:
       - "3893:3893"
     volumes:
       - ./glauth/config.toml:/app/config/config.cfg:ro
+    networks:
+      - scadalink-net
     restart: unless-stopped
 
   mssql:
@@ -40,6 +44,8 @@ services:
       - scadalink-mssql-data:/var/opt/mssql
       - ./mssql/setup.sql:/docker-entrypoint-initdb.d/setup.sql:ro
       - ./mssql/machinedata_seed.sql:/docker-entrypoint-initdb.d/machinedata_seed.sql:ro
+    networks:
+      - scadalink-net
     restart: unless-stopped
 
   smtp:
@@ -52,6 +58,8 @@ services:
       MP_SMTP_AUTH_ACCEPT_ANY: 1
       MP_SMTP_AUTH_ALLOW_INSECURE: 1
       MP_MAX_MESSAGES: 500
+    networks:
+      - scadalink-net
     restart: unless-stopped
 
   restapi:
@@ -62,7 +70,14 @@ services:
     environment:
       API_NO_AUTH: 0
       PORT: 5200
+    networks:
+      - scadalink-net
     restart: unless-stopped
 
 volumes:
   scadalink-mssql-data:
+
+networks:
+  scadalink-net:
+    name: scadalink-net
+    external: true