chore(docker): tune production stack for 2C8G hosts

Add mysql-prod-2c8g.cnf, container mem/cpu limits, Redis maxmemory,
and default Nexus pool 30/20 for 8GiB 1Panel deployments.

docker/docker-compose.prod.yml

@@ -1,4 +1,6 @@
 # Nexus 6.0 — production Compose (1Panel / bare Docker host)
+# Tuned for 2 vCPU / 8 GiB — see docker/mysql-prod-2c8g.cnf
+#
 # Usage:
 #   cp docker/.env.prod.example docker/.env.prod   # fill secrets from Baota .env
 #   docker compose -f docker/docker-compose.prod.yml --env-file docker/.env.prod up -d --build
@@ -18,6 +20,9 @@ services:
       MYSQL_PASSWORD: ${MYSQL_PASSWORD:?set MYSQL_PASSWORD}
     volumes:
       - mysql-data:/var/lib/mysql
+      - ./mysql-prod-2c8g.cnf:/etc/mysql/conf.d/99-nexus-2c8g.cnf:ro
+    mem_limit: 2g
+    cpus: 1.5
     healthcheck:
       test: ["CMD-SHELL", "mysqladmin ping -h 127.0.0.1 -uroot -p\"$$MYSQL_ROOT_PASSWORD\" || exit 1"]
       interval: 10s
@@ -30,9 +35,18 @@ services:
   redis:
     image: redis:7-alpine
     restart: unless-stopped
-    command: ["redis-server", "--appendonly", "yes"]
+    command:
+      - redis-server
+      - --appendonly
+      - "yes"
+      - --maxmemory
+      - 256mb
+      - --maxmemory-policy
+      - allkeys-lru
     volumes:
       - redis-data:/data
+    mem_limit: 384m
+    cpus: 0.5
     healthcheck:
       test: ["CMD", "redis-cli", "ping"]
       interval: 10s
@@ -70,9 +84,13 @@ services:
       NEXUS_API_KEY: ${NEXUS_API_KEY:?set NEXUS_API_KEY}
       NEXUS_ENCRYPTION_KEY: ${NEXUS_ENCRYPTION_KEY:-}
       NEXUS_API_BASE_URL: ${NEXUS_API_BASE_URL:?set NEXUS_API_BASE_URL}
+      NEXUS_DB_POOL_SIZE: ${NEXUS_DB_POOL_SIZE:-30}
+      NEXUS_DB_MAX_OVERFLOW: ${NEXUS_DB_MAX_OVERFLOW:-20}
     volumes:
       - nexus-state:/var/lib/nexus
       - nexus-web-data:/app/web/data
+    mem_limit: 2g
+    cpus: 1.5
     healthcheck:
       test: ["CMD", "curl", "-sf", "http://127.0.0.1:8600/health"]
       interval: 30s