feat: add Promtail, Loki, and Grafana log aggregation stack (refs #86)

- Add Promtail for Docker log scraping with container discovery
- Add Loki for log storage with 30-day retention
- Add Grafana with Loki datasource auto-provisioned
- Add IP whitelist middleware restricting Grafana to RFC1918 ranges
- Container count: 6 → 9

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -264,6 +264,84 @@ services:
         max-size: "10m"
         max-file: "3"
 
+  # Log Aggregation - Loki
+  mvp-loki:
+    image: grafana/loki:2.9.0
+    container_name: mvp-loki
+    restart: unless-stopped
+    volumes:
+      - ./config/loki/config.yml:/etc/loki/config.yml:ro
+      - mvp_loki_data:/loki
+    command: -config.file=/etc/loki/config.yml
+    networks:
+      - backend
+    healthcheck:
+      test: ["CMD-SHELL", "wget -q --spider http://localhost:3100/ready || exit 1"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
+
+  # Log Aggregation - Promtail
+  mvp-promtail:
+    image: grafana/promtail:2.9.0
+    container_name: mvp-promtail
+    restart: unless-stopped
+    volumes:
+      - ./config/promtail/config.yml:/etc/promtail/config.yml:ro
+      - /var/lib/docker/containers:/var/lib/docker/containers:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+    command: -config.file=/etc/promtail/config.yml
+    networks:
+      - backend
+    depends_on:
+      - mvp-loki
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
+
+  # Log Aggregation - Grafana
+  mvp-grafana:
+    image: grafana/grafana:10.0.0
+    container_name: mvp-grafana
+    restart: unless-stopped
+    environment:
+      GF_SECURITY_ADMIN_PASSWORD: ${GRAFANA_ADMIN_PASSWORD:-admin}
+      GF_USERS_ALLOW_SIGN_UP: "false"
+    volumes:
+      - ./config/grafana/datasources:/etc/grafana/provisioning/datasources:ro
+      - mvp_grafana_data:/var/lib/grafana
+    networks:
+      - backend
+      - frontend
+    depends_on:
+      - mvp-loki
+    healthcheck:
+      test: ["CMD-SHELL", "wget -q --spider http://localhost:3000/api/health || exit 1"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+    labels:
+      - "traefik.enable=true"
+      - "traefik.docker.network=motovaultpro_frontend"
+      - "traefik.http.routers.grafana.rule=Host(`logs.motovaultpro.com`)"
+      - "traefik.http.routers.grafana.entrypoints=websecure"
+      - "traefik.http.routers.grafana.tls=true"
+      - "traefik.http.routers.grafana.tls.certresolver=letsencrypt"
+      - "traefik.http.routers.grafana.middlewares=grafana-ipwhitelist@file"
+      - "traefik.http.services.grafana.loadbalancer.server.port=3000"
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
+
 # Network Definition
 networks:
   frontend:
@@ -302,3 +380,7 @@ volumes:
     name: mvp_postgres_data
   mvp_redis_data:
     name: mvp_redis_data
+  mvp_loki_data:
+    name: mvp_loki_data
+  mvp_grafana_data:
+    name: mvp_grafana_data